Rub the cold butter into the wholewheat flour and salt until crumbly. Add cold water a spoon at a time and bring together into a dough. Wrap and chill for 30 minutes.

Heat the olive oil and cook the onion gently until soft and golden, about 10 minutes — caramelizing it here adds a lovely sweetness. Add the garlic and thyme and cook for a minute more.

Turn up the heat, add the mushrooms, and cook until they release and lose their liquid, about 8 to 10 minutes. Pour in the white wine and let it bubble away, then let the filling cool slightly.

In a bowl, mix the ricotta, grated cheese, egg, dill, salt, and pepper. Stir in the cooked mushrooms and onion.

Roll the dough into a rough circle about 12 inches wide on parchment paper. Pile the filling in the center, leaving a 2-inch border.

Fold the edges of the dough up and over the filling, pleating as you go. Brush the crust with egg yolk or plant milk.

Bake at 390°F (200°C) for 30 to 35 minutes, until the crust is golden and the filling is set. Cool slightly before slicing.

For a wild mushroom galette, use a mix of wild or exotic mushrooms and add a small handful of soaked, chopped dried porcini, cooking the filling in the strained soaking liquid.