Combine the crepe ingredients in a blender and let them stand for 30 minutes.

In an 8-inch nonstick skillet, melt 1/2 a tablespoons of butter over moderately high heat. Pour in enough batter to just coat the bottom of the skillet, swirling, and cook it undisturbed until the top is set and the bottom is golden. (Do not turn it over.) Transfer the crepe to paper towels in one layer, with the golden side down. Make more crepes with the remaining batter. Use more butter as needed.

Mix all the cheese filling ingredients together in a large bowl. With a large spoon, place 3 tablespoons of filling in the center of each crepe; fold the opposite sides of the crepe over the filling until the sides barely touch. Fold in the ends to completely enclose the filling, forming packets. Heat butter in a frying pan on medium heat, and place 6 blintzes in the pan. Cook on both sides until they are golden. Repeat with the remaining blintzes. Serve them warm with sour cream and/or preserves on the side. Serves 6 (12 blintzes).