Step 1

Parboil potatoes for 6-10 minutes, depending on size, so that they are partially cooked but still firm enough to grate. I used two large (200 g / 7 oz each) potatoes so I boiled mine for 10 minutes. You can peel first them if you like, I didn't bother. Rinse in cold water and set aside to cool.

Step 2

Prep your mushrooms, I sliced shiitake and chestnut mushrooms into thick slices and tore large oyster mushrooms into 2 pieces with my hands so that my filling has a variety textures.

Step 3

Preheat a 26 cm / 10 inch heavy oven proof skillet, add 15 ml / 1 tbsp of olive oil and chopped shallots. Sauté on low heat until almost transparent, the add 2 sliced garlic cloves and fresh thyme. Carry on sautéeing until cooked, then remove from the pan.

Step 4

Increase the heat and add about half of the mushrooms to the skillet with a pinch of salt. Allow the water to cook out and for the mushrooms to turn brown. Remove from the pan and add the rest of the mushrooms. When the second batch is done, return the first portion of mushrooms to the pan and stir in 15 ml / 1 tbsp of olive oil. Allow mushrooms to char in places then remove from the pan.

Step 5

Return shallot mixture to the pan, add lentils, 240 ml / 1 cup of oat cream and 120 ml / ½ cup of water (or 1½ cups of oat milk instead). Dilute cornstarch in a bit of liquid first, then stir in miso, wholegrain mustard and freshly grated clove of garlic - add all of this to the dish. Season with black pepper and soy sauce. And you may want to add a touch more salt but do taste first.

Step 6

Preheat the oven to 200° C / 390° F (or 180° C / 350° F with a fan on).

Step 7

Grate parboiled potatoes coarsely - I used a food processor but you can also do that by hand. Place grated potatoes in a mixing bowl. Using your hands, toss them in 2 tbsp of olive oil, 1 tbsp of cornstarch and ½ tsp of salt.

Step 8

Spread potato mixture on top of the pie leaving a thin margin all around. Bake until the filling is bubbling hot and the rosti is crispy and golden - about 40 minutes. Consume immediately.