Mushroom tarts

These were a riff on one of my favorite Deborah Madison recipes for tomato/olive/rosemary tarts. Since I had to miss an Easter brunch to which I was supposed to bring stuffed mushrooms for nine people, I had kind of a lot of mushrooms to use up. I'd always meant to play around with other fillings for this dough and I had a friend coming over for dinner last Saturday, so I put these together. I use all all-purpose flour when making the tomato variation, but thought that the strong, earthy mushroom flavors would benefit from some whole wheat flour in the crust. They were fantastic both hot out of the oven and at room temperature for lunch at work and they kept pretty well. I made them on Saturday and just ate the last one today, Thursday.
I don't really have a recipe for the filling, but what I did, more or less, was: brown an onion in butter, then saute about a pound and a half of finely chopped mushrooms with a splash of wine and some thyme, then stir in a spoonful or two of sour cream to bind it together and salt to taste. I happened to have some olives around and chopped up about 1/3 c. to put on top.

Galette dough
1 c. whole wheat flour
1 c. unbleached all-purpose flour
1/2 t. salt
12 T cold, unsalted butter, cut into chunks
1/3–1/2 c. ice water

Preheat the oven to 425F. Mix flour and salt together. Cut in the butter with a pastry cutter, two knives, or your hands, leaving some pea-sized pieces. Sprinkle the ice water over by the tablespoonful and toss until you can bring the dough together into a ball. Press it into a disc and refrigerate for 15 minutes.

Divide the dough into 6 equal parts and roll or pat into a circle roughly 8" in diameter. Spoon 1/6th of the filling into the center and spread out to about an inch from the edge. Sprinkle chopped olives on top of the mushrooms and drizzle with walnut or olive oil. Fold the edges of the dough over the mushrooms, creasing every inch or so. Bake until crust is golden, about 20–25 minutes.