Combine wrapper ingredients in a blender, or in a bowl with an immersion blender, or whisk by hand until smooth. Cover with plastic wrap and refrigerate for an hour or up to two days.

Heat a medium skillet or crêpe pan over medium-high heat. Once heated, brush pan lightly with melted butter or oil. If batter has gotten too thick to pour thinly in the fridge, you can add an additional tablespoon or two of milk or water to thin it. Pour 3 to 4 tablespoons batter into skillet, just enough that it coats the bottom in an even layer when you swirl it around. Let cook, undisturbed, until the crêpe becomes a little golden underneath or at the edges.

Use a small offset spatula to loosen the edges and get underneath the crêpe enough to lift it. Flip the crêpe in one movement. Cook the crêpe on the reverse side for another 20 seconds, then slide onto a plate to cool. Repeat with remaining batter.

Mix all filling ingredients together until smooth. Place 3 tablespoons or so filling across the center of the top wrapper/crêpe in your stack. Fold the bottom part of the wrapper up and over it; fold the sides in over the bottom and filling, then fold the pancake up to form an egg roll-like shape filled pancake.

Heat a pat of butter over medium heat in a skillet. Fry blintz until browned on both sides. Transfer to a plate and serve with sour cream or a fruit sauce or jam of your choice.