In a medium saucepan, melt 2 tablespoons of butter over medium heat. Sauté 1 diced onion and 1 chopped celery stalk until golden and fragrant, about 5 minutes. Gradually add 1 cup of milk, heating until hot (but not boiling). Stir in 2 tablespoons of chopped cilantro or parsley, 1 teaspoon of hot pepper sauce, and season with salt, white pepper, and a pinch of nutmeg. Mix 2 tablespoons of cornstarch with 2 tablespoons of water and stir into the hot mixture until thickened. Fold in 2 cups of cooked protein and heat through, then let cool slightly.

In a saucepan, combine 1 cup of milk, 2 tablespoons of butter, and a pinch of salt. Heat over medium heat until the mixture is scalding, just before boiling. Gradually add 2 cups of flour, stirring vigorously with a wooden spoon until a dough forms. Continue stirring until the mixture pulls away from the sides of the pan. Turn the dough onto a floured surface and knead briefly until smooth, about 1-2 minutes, then cover to rest.

Roll out the prepared dough on a floured surface to about ¼-inch thickness. Use a round cutter or glass to cut out circles, approximately 3-4 inches in diameter. Place 1 tablespoon of the cooled filling in the center of each circle. Fold the dough over to create a half-moon shape and press the edges to seal securely, ensuring no filling escapes. Use a fork to crimp the edges for a decorative touch.

In a deep skillet or frying pan, heat 2-3 inches of oil over medium heat until it reaches 350°F (175°C). Working in batches, carefully place the assembled rissois in the hot oil, frying them for about 3-4 minutes per side or until golden brown and crisp. Use a slotted spoon to transfer the cooked rissois to a paper towel-lined plate to absorb excess oil. Serve hot or allow to cool completely before transferring to the freezer for later enjoyment.