Mushroom Slice Recipe

Make dough

In a large bowl or food processor, combine 1.5 cups flour, 1 tsp salt and 0.5 tsp sugar. Cut in 6 tbs cold cubed butter using a pastry cutter or pulse in the processor until mixture resembles coarse crumbs with pea-sized pieces.

Sprinkle 3 tbs cold water over the flour-butter mixture, gently mix with a fork until dough just comes together. If dough is still dry, add up to 1 additional tablespoon cold water.

Form the dough into a flat disc, wrap in plastic wrap and chill in the refrigerator for 20–30 minutes while you prepare the filling.

Preheat the oven to 190°C (375°F). Lightly grease an 8x8-inch (or similar) baking pan or line it with parchment paper, leaving an overhang for easy removal.

Roll out the chilled dough on a lightly floured surface to a rectangle slightly larger than the pan. Transfer to the pan, pressing to fit and trimming or folding edges to create an even base and a small rim. Refrigerate while making the filling.

Heat a large skillet over medium heat. Add 2 tbs olive oil and 1 tbs butter. When butter foams, add 1 cup finely chopped onion and sauté for 4–5 minutes until soft and translucent.

Add 2 tsp minced garlic and cook 30 seconds until fragrant, stirring so it doesn’t brown.

Add 4 cups sliced mixed mushrooms in a single layer as much as possible. Cook undisturbed for 3–4 minutes to allow browning, then stir and continue cooking another 4–6 minutes until the mushrooms have released their liquid and are golden.

Stir in 1 tbsp fresh thyme leaves. If using, pour in 2 tbs white wine and scrape any browned bits from the pan; let it reduce for 1–2 minutes.

Sprinkle 1 tsp flour over the mushrooms and stir to incorporate; cook 1 minute to remove raw flour taste.

Add 0.5 cup stock and 0.25 cup heavy cream, stirring to combine. Simmer 2–3 minutes until mixture thickens slightly.

Season the filling with 1 tsp salt, 0.5 tsp freshly ground black pepper and 1 tsp soy sauce or tamari. Taste and adjust seasoning.

Remove from heat and stir in 1 cup shredded Gruyère (reserve a small handful for topping) and 2 tbs chopped fresh parsley. Let the filling cool for 5–10 minutes so it firms slightly before assembling.

Remove the chilled crust-lined pan from the fridge. Spoon the mushroom filling into the prepared crust and spread evenly, pressing down lightly so the filling is compact.

Whisk together 1 large egg and 1 tsp milk to make an egg wash. Brush the exposed crust edges lightly with the egg wash and sprinkle reserved shredded cheese on top of the filling and optional sesame seeds or flaky sea salt on the crust edges.

Bake in the preheated 190°C (375°F) oven for 30–35 minutes, until the crust is golden and the filling is bubbling and set. If the crust edges brown too quickly, tent loosely with foil after 20 minutes.

Remove from oven and let the mushroom slice cool in the pan on a wire rack for 10–15 minutes. This helps the filling set for cleaner slices.

Use the parchment overhang to lift the slice from the pan. Transfer to a cutting board, slice into 6–8 portions and garnish with extra chopped parsley if desired. Serve warm or at room temperature.