Dried Mushrooms

*Blini with Caviar* 2 1/4 teaspoons active dry yeast (one 1/4-ounce envelope) 1/2 cup warm water (110 degrees) 1 cup all-purpose flour Coarse salt 1/2 cup low-fat buttermilk 1 tablespoon unsalted butter, melted, plus more for pan 1/2 teaspoon sugar 2 large eggs, separated Garnish: Creme fraiche and salmon or trout roe Sprinkle yeast over water. Let stand until foamy, about 5 minutes. Stir together flour and 1/2 teaspoon plus a pinch of salt. Stir together buttermilk, butter, sugar, and egg yolks