In a blender, combine the milk, eggs, sugar, salt, chestnut flour, and sweet rice flour. Blend on low to combine, scraping down the sides of the blender once or twice. With the motor running, blend in the melted butter. Pour the batter into a measuring pitcher or bowl; thin with a little more milk if the batter is too thick. Have a large plate by the stove on which to stack the cooked crepes.
To make the filling, in a medium bowl, stir together the cheese, sugar, egg yolk and salt. Quickly stir in the melted butter. Chill until needed.
To fry the crepes, heat an 8-inch (20-cm) crepe pan or skillet over medium heat, and use a scrunched-up paper towel to swipe it with a bit of ghee or butter. (Too much butter will cause the batter to slip as you swirl it to coat the pan.)
Pour a scant 1⁄4 cup (59 ml) of batter onto the crepe pan, tilting, swirling and shuffling to coat it evenly with a thin layer of batter. Cook the crepe until just barely set on top, 30–60 seconds. Use a thin, metal spatula to ease the edges of the crepe up off the pan, then slide (or drag) the crepe onto the plate, cooked side down. It should be barely colored on the bottom.
Continue cooking the crepes, swiping the pan with a bit of butter between crepes, and adjusting the heat so that the pan doesn’t burn but the crepes cook in 30–60 seconds each.
To fill the blintzes, place 2 1⁄2 tablespoons (38 g) of cheese filling on the lower third of a crepe and fold the bottom up over the cheese. Fold the sides in so that they just touch, then roll the blintz up from the filled end up to form a parcel—it should look something like an egg roll. Stack the filled blintzes on a plate.
When the blintzes have all been filled, melt some butter or ghee in your crepe pan over medium-low heat (or use another large skillet if you like). Fry the blintzes until they are golden on the bottom, about 2 minutes, then flip and brown on the second side, another 2 minutes. Have the heat low enough so that the filling heats through without the bottoms burning.
Serve the warm blintzes with the applesauce, maple syrup, and a dollop of sour cream.
Extra blintzes keep brilliantly, fried or unfried, in the refrigerator for up to 3 days or in the freezer for up to 2 months.