Potato Tart with Caramelized Onions and Mushrooms

Thinly slice onions and add to a pan with olive oil.

Stir the onions occasionally until they cook down and get jammy and golden.

Spread the mashed potatoes into the pie dough.

Sprinkle on the goat cheese.

Add the browned mushrooms.

Add the caramelized onions evenly over the top.

Fold the excess dough towards the center.

Brush the dough with egg wash.