Add buckwheat and all-purpose flours, milk, eggs, salt, and melted butter to a blender and blend until smooth. Let the batter rest for at least 30 minutes in the refrigerator.
Lightly butter a medium pan and warm over medium heat. Pour 1⁄4 cup of batter into the pan, swirling to coat the bottom evenly. Cook for 1 to 2 minutes, or until the blintz begins to set and the edges curl. Flip and cook for 30 more seconds. Transfer to a plate and repeat process with remaining batter.
Lay blintzes on a flat surface. Dollop about 2 tablespoons of cream cheese filling in the center of each and spread evenly. Roll them into a burrito shape.
Warm a nonstick pan over medium heat and add around 1⁄2 tablespoon of butter. Place the filled blintzes, seam side down, in the pan and cook for 1 to 2 minutes on each side, or until light golden brown and warmed through.
Arrange the blintzes on a plate and top with date butter, a drizzle of honey, and a sprinkle of toasted pistachios.