To make creme fraiche, heat whipping cream in a small saucepan over low heat until warm (90 degrees F to 100 degrees F). Pour into a small clean jar. Stir in buttermilk, screw on jar lid, and let the mixture stand at room temperature for 24 to 30 hours or until thickened. Do not stir. Store, covered, in the refrigerator up to 1 week.

Combine flour and yeast in a mixing bowl. Heat and stir the 1 cup milk, butter or margarine, sugar, and salt in a small saucepan until warm (120 degrees F to 130 degrees F) and butter is almost melted. Add to the flour mixture with egg yolk. Beat with an electric mixer on low speed for 30 seconds, then on high speed 3 minutes, scraping bowl frequently. Cover batter and let rise in a warm place until nearly double (45 to 60 minutes).

Stir the 1/3 cup hot milk into the batter. Beat egg white in a clean medium bowl with an electric mixer on high speed until stiff peaks form (peaks stand straight). Fold into batter. Cover and let rise 30 to 40 minutes more until light.

For each pancake, pour about 2 tablespoons of batter onto a lightly greased or buttered hot griddle or heavy skillet. Cook until golden; turn, using a spatula, and cook until done.

Transfer blini to a warm platter in a 300 degree F oven as they are cooked; cover with foil. Serve immediately with creme fraiche or sour cream, caviar, and, if desired, chopped hard-cooked eggs, finely chopped red onion, and lemon wedges. Makes about 8 servings (2 blini each).

Prepare batter, except for egg white; cover and refrigerate up to 1 day. Fold in beaten egg white just before baking.