To make the pancake batter, whisk together the milk, eggs, oil and salt in a large bowl. Add the flour gradually, whisking constantly until the batter is smooth. Set aside. Stir together all of the filling ingredients in a small bowl. Set aside. Set an 8-inch frying pan (I used a non-stick crepe pan) on medium heat. When the pan is hot, add a swipe of butter. Pour in 2 to 3 tablespoons of the pancake batter, swirling the pan to create a thin pancake. (If the batter seems to thick and you have trouble swirling it evenly in the pan, whisk in a little more milk.) Cook the pancake about 30 seconds, until the top looks dry and the edges start to curl. Use your fingers or a spatula to remove the pancake and set aside on a plate to cool. Then, make as many more pancakes as the batter will allow. Let the pancakes cool a little. Lay out about 4 pancakes, pale side up, and put about 1 1/2 tablespoons of the filling in the center of each. Fold each of the pancakes up into a square package, making sure the corners are completely closed. Heat 2 teaspoons vegetable oil and 1 1/2 tablespoons butter in a large frying pan over medium heat. Cook the blintzes in batches until deep golden brown and warmed through, 2 to 3 minutes per side. Sprinkle with powdered sugar and serve with applesauce on the side if you like.