Combine remaining syrup with cornstarch, lemon peel, nutmeg and salt.
Cook and stir until thickened; add blackberries and heat thoroughly.
Serve over cheese blintzes. Garnish with dollop of sour cream mixture.
Cheese Blintzes: Combine 3/4 cup flour and 1/4 teaspoon salt. Combine 1 cup milk and 2 eggs; gradually add to flour mixture and beat until smooth. For each of 6 blintzes, pour about 1/4 cup batter into lightly oiled, 8 inch skillet; rotate skillet to spread batter evenly over surface. Cook over medium heat until edges begin to pull away from sides of skillet and bottom of blintze is lightly browned. Combine 1 egg, 1 1/2 cups ricotta cheese*, 1 to 3 teaspoons sugar, 1/2 teaspoon vanilla and dash ground nutmeg; mix well. Place 1/4 cup cheese filling in center of browned side of each blintze. Overlap opposite sides over filling to form rectangular, enclosed packet. Brown lightly on both sides in butter. Makes 6 blintzes.
Do-Ahead Tip: Blintzes can be frozen before filling or can be filled, folded and frozen. Thaw; then continue as instructed above.
*Well drained small curd cottage cheese can be substituted for the ricotta cheese.