Mashed Potato Gratin

Cheesy, creamy mashed potatoes topped with garlic parmesan potato gratin – this truly is the ultimate side dish!

I spotted the ever-so-iconic Chef John post these and I’ve never seen anything more beautiful in my whole life. Grab your eating pants and follow me, because things about to get real delicious real quick.

Cheesy Mashed Potatoes

The first layer of this beautiful creation is mashed potato. I know everyone may already have their own ‘go-to’ mash recipe, which you’re welcome to use, but here are the usual suspects in mine:

• Butter – and lots of it!
• Cream – or you could use whole milk.
• Cheese – I use cheddar, but you could use comte or gruyere.
• Seasoning – potatoes LOVE salt so don’t hold back!

You’ll want to start off with cold water and bring to a boil, as this will help the potatoes cook through evenly. From there, drain them and let them sit for 1 minute. This will help some of the moisture escape and prevent the mash from being watery.

During this time I recommend melting the butter and warming the cream using the residual heat in the pot. Doing this will help the potatoes absorb both of them without turning the mash clumpy.

Process shots: boil potatoes (photo 1), drain (photo 2), warm butter and cream (photo 3), add potatoes (photo 4), mash (photo 5), mash in cheese and seasoning (photo 6).

Potato Gratin

On top of the mash goes a potato gratin i.e. thinly sliced and stacked potatoes. To ramp up the flavour I love adding in some garlic and parmesan, just to make the topping extra special.

Do I have to pre-cook the potatoes on top?

Nope! They cook through in the oven and crisp up beautifully. If you slice them thinly they’ll be perfectly tender by the time the whole thing is done.

Process shots: peel potato (photo 1), halve (photo 2), thinly slice (photo 3), melt butter then add garlic and seasoning (photo 4), toss in potatoes (photo 5), toss in parmesan (photo 6).

Mashed Potato Gratin

To combine everything, just plonk the mash in a baking dish and level off with a spoon or spatula. From there, you can top with the garlic parmesan potatoes. You’ll want to stack them fairly tightly and at a slight angle.

To bake the whole thing, I find the best method is to do a portion of the cooking with foil on, then remove it for the bulk of the time. The foil will trap the steam and help the potatoes cook through without them browning too quickly.

Process shots: add mash to baking dish (photo 1), stack potatoes (photo 2), bake with foil (photo 3), remove, top with parmesan and bake again (photo 4).

Mashed Potato Gratin FAQ

What kind of potatoes should I use?

Use a floury/baking potato such as a Maris Piper (UK) or Russet (US). Or simply ones in the store that say ‘Baking Potatoes’. These will give the best texture for both the mash and gratin.

Do I have to add the garlic?

Nope! You can leave this out if you’d prefer.

How do I make sure the potatoes are cooked through?

If they’re sliced thinly and you bake for the full hour, they will be fork tender. If they’re not, just add the foil back on and continue baking.

Serving Mashed Potato Gratin

Once out of the oven it’s essential that you let it rest. This will not only allow the mash to retain its shape, but it’ll also give time for the gratin to finish cooking through.

I love to finish with some fresh chives, but they’re optional. This is the perfect Side for just about everything and works perfect as part of a Roast Dinner!

Alrighty, let’s tuck into the full recipe for this mashed potato gratin shall we?!

How to make Mashed Potato Gratin (Full Recipe & Video)

Mashed Potato Gratin

Cheesy, creamy mashed potatoes topped with garlic parmesan potato gratin - this truly is the ultimate side dish!

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Servings (click & slide): 6 - 8

Course: Side Dish

Cuisine: American / French

Prep Time: 20 minutes minutes

Cook Time: 1 hour hour 30 minutes minutes

Total Time: 1 hour hour 50 minutes minutes

Calories per serving: 485kcal

Author: Chris Collins

Cost per serving: £2 / $2.50

Equipment:

• Potato Peeler
• Sharp Knife & Chopping Board
• Large Pot & Colander
• Wooden Spoon & Potato Masher
• Box Grater
• 25cm x 17cm / 10" x 6.5" Baking Dish (or similar size)
• Large Mixing Bowl
• Aluminium Foil

Ingredients (check list):

Mashed Potatoes

• ▢ 1.5kg / 3.3lb Baking Potatoes (see notes)
• ▢ 1 tbsp + 1 tsp Salt, or to taste
• ▢ 6 tbsp / 90g Butter, leave at room temp
• ▢ 160ml / 2/3 cup Cream, leave at room temp
• ▢ 150g / 1 1/2 cups Cheddar, grated
• ▢ 1/4 tsp Black Pepper, or to taste

Potato Gratin

• ▢ 750g / 1.6lb Baking Potatoes
• ▢ 2 tbsp / 30g Butter
• ▢ 1 large clove of Garlic, finely grated/minced
• ▢ 1/4 - 1/2 tsp Salt, or to taste
• ▢ 1/8 - 1/4 tsp Black Pepper, or to taste
• ▢ 40g / 1.4oz Parmesan (see notes)
• ▢ finely diced Fresh Chives, to garnish

Instructions:

• For the mash, peel and dice the potatoes into chunks, then place them in a large pot of cold water. Stir in 1 tbsp salt and turn the heat to high. Bring to a boil, then cook the potatoes until knife tender (but not so soft they're falling apart). Drain in a colander and leave for 1 minute.
• Immediately add the butter and cream to the pot and stir to melt the butter. The residual heat from the pot should be able to do this, but if not just momentarily turn on the heat to help things along. Add the drained potatoes and mash until smooth. Mash in the cheese then season with salt and pepper (I typically end up with 1 tsp salt and 1/4 tsp pepper, but work to taste).
• Spoon into a 25cm x 17cm / 10" x 6.5" baking dish (or similar size) and level off with a spoon. Preheat the oven to 200C/400F.
• For the gratin, peel the potatoes and slice them in half lengthways. Place each piece flat side down and very thinly slice into half moons (around 1/8").
• Place the butter in a large mixing bowl and melt in the microwave. Whisk in the garlic, salt and pepper, then toss in the sliced potato. Finally, toss in half of the parmesan until well coated.
• Layer the slices cut-side-down on top of the mashed potato in 3 rows and at a slight angle (see video for reference). Cover with foil and bake for 20 minutes. Remove the foil, sprinkle over the rest of the parmesan and bake again for 40 minutes. The top should be deep golden and crisp, with the potatoes knife tender.
• Leave to rest for 15-20 minutes to allow the mash to retain its shape and for the sliced potatoes to finish cooking on top (it'll stay piping hot - promise). Garnish with chives, then tuck in and enjoy!

Quick 1 min demo!

Notes:

a) Potatoes - Use a floury/baking potato such as a Maris Piper (UK) or Russet (US). Or simply ones in the store that say 'Baking Potatoes'. These will give the best texture for both the mash and gratin.

b) Parmesan - I typically buy the 'dusty' pre-packaged stuff from the fridge section (don't use the non-fresh stuff). If you've just got a block of parmesan, use the most coarse side of the box grater to replicate the dusty texture. This will ensure it gets well distributed through the slices.

c) Cooking times / texture - After 1 hour of baking the potatoes on top should be a touch al dente but still knife tender. They'll soften a little more as they rest. If for whatever reason they're still needing a bit longer, consider covering with foil and baking a little longer. You should need to do this though if the potatoes are sliced thinly - just an emergency step!

d) Inspiration - The inspiration behind this recipe is credited to the awesome Chef John!

e) Calories - Whole recipe divided by 8.

Your Private Notes:

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Nutrition:

Nutrition Facts

Mashed Potato Gratin

Amount Per Serving

Calories 485 Calories from Fat 242

% Daily Value*

Fat 26.85g41%

Saturated Fat 16.338g82%

Trans Fat 0.73g

Polyunsaturated Fat 1.165g

Monounsaturated Fat 7.048g

Cholesterol 81mg27%

Sodium 690mg29%

Potassium 1228mg35%

Carbohydrates 50.82g17%

Fiber 6.2g25%

Sugar 2.82g3%

Protein 12.17g24%

Vitamin A 888IU18%

Vitamin C 55.6mg67%

Calcium 221mg22%

Iron 2.28mg13%

* Percent Daily Values are based on a 2000 calorie diet.

Looking for more?You'll find plenty more delicious comfort food like this in my Debut Cookbook 'Comfy'