In a mixing bowl combine flour, granulated sugar, baking powder, and salt. In another mixing bowl, beat milk, water, eggs, and vanilla until well combined. Add to flour mixture; beat until smooth.
Heat a lightly greased 6-inch skillet over medium heat until a few drops of water dance across the surface. Remove skillet from heat. For each blintz, spoon a scant 2 tablespoons batter into hot skillet. Quickly lift and tilt skillet to spread batter into a thin, even circle. Cook about 1 minute or until top is set and edges are lightly browned. Invert skillet to remove blintz. Repeat with remaining batter, greasing skillet occasionally, to make 16 blintzes.
For filling, combine strawberry cake-and-pastry filling, nuts, and amaretto; stir until well combined.
To assemble, spray a 13x9x2-inch baking pan with nonstick spray. Place blintzes on a work surface, browned sides down; spoon about 1-1/2 tablespoons of the filling in the middle of each blintz. Fold the top edge of each blintz over filling. Fold sides over, then fold bottom edges up over all. Place blintzes, seam sides down, in prepared baking pan. Brush with melted margarine. Bake in a 400 degree F oven for 20 to 25 minutes or until heated through. If desired, top with powdered sugar and serve with sour cream or whipped cream. Makes 8 servings.