Makes enough for 12 cupcake-size tarts, but for the shallower, wider, tarts, I'm not certain.
Defrost
2 sheets puff pastry
Preheat oven to 435.
Cook
12-16 oz mushrooms in a little oil
until they've stopped 'sweating' but are not completely dried out.
Defrost
1 package frozen chopped spinach
and drain it, pressing out some of the liquid. Add it to the mushrooms.
Grate
1-2oz swiss cheese and set aside
Prepare a roux by heating, in a 2qt saucepan,
2T butter
and adding
2T flour
and cooking until the flour loses its raw flavor, but before it really starts to brown.
Add
1/2 c milk
slowly, whisking to avoid lumps, to make a thick sauce. Season with
salt
pepper
freshly grated nutmeg -- perhaps 1t
Let cool a little, then stir in the mushroom/spinach mix, and then the swiss cheese.
Beat until nicely aerated
1 egg
and mix it into the filling.
Separate
1 egg
discarding the white and keeping the yolk. Add
1t water
to the yolk and mix to thin it.
Roll out
the puff pastry
into a 60-degree parallelogram so that you can get 6 rounds, each about 4 1/2 inches in diameter (our tiny corningware bowls make a good template), from each sheet. Re-chill if it's no longer cool to the touch. Then cut out the disks, and fill each container (in a shallow mold or a cupcake mold) with one sheet, folding the vertical edges as needed to make a cup. Brush the top edge of each with the egg wash mixture.
Fill the tart cups with 1/12 of the batter each. Cook about 11 minutes.
Sprinkle the tarts with a little bit of grated parmesan or grated swiss if you like.