In a blender, combine the eggs, milk, flour, sugar and salt. Blend until the mixture forms a smooth batter. Heat a 10-inch nonstick skillet over medium-low heat. Melt 1 cube of butter in the pan. Add 1/4 cup of batter and quickly tilt the pan to form an even coating of batter on the bottom of the pan. Cook for 1 minute, until set and slightly browned. Using a heat-resistant spatula, carefully loosen the sides and gently flip the crepe over. Cook for 1 minute. Repeat with the remaining batter and butter, stacking the crepes on top of each other on a plate as they are ready. You should have 8 or 9 crepes total. Add 1 tablespoon of peanut butter to each crepe and, using the back of a spoon, spread evenly over the crepes, leaving a 1/2-inch border. Spread 2 teaspoons of jam over the peanut butter. Line 5 to 6 blueberries along the center of each crepe. Fold the crepe in half over the blueberries. Fold the two ends inward and continue to roll into a tube shape. Repeat with the remaining ingredients. Cut each crepe in half horizontally and arrange on a platter. Dust with confectioners' sugar.