Mashed Potato Gratin

overhead shot of mashed potato au gratin fresh out the oven garnished with chives

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5 from 8 votes

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

Prep Time20

Cook Time1 30

Total Time1 50

Course: Side Dish

Cuisine: American, French

Servings: - 8

Author: Chris Collins

Cost: £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

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!

Video

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.

Nutrition