Sweat the greens and onion in the butter and oil in a heavy covered pan over low heat for 40 to 45 minutes, stirring occasionally, until they are very tender. Season with salt and cool to room temperature. Finely chop the vegetables and, using your hands, mix in the cheese. Add more salt if needed. Roll into 1-inch-diameter balls, approximately 10 to 12 grams each, cover with plastic wrap, and reserve in the refrigerator for up to 1 week.
Sprinkle the yeast over the warm milk and set aside in a warm place for about 10 minutes to activate. Combine the dry ingredients. Add the yeast mixture to the egg white. Whisk in the dry ingredients and mix until the batter is smooth. Proof at room temperature for about 1 hour. Extra batter—enough to coat a second batch of Beignet Centers—will hold for a few days in the refrigerator. Bring to room temperature before using.
Preheat the oven to 325°F (165°C). If you have a convection oven, set the fan on low.
Gently toss the kale leaves with just enough olive oil to coat them with a light film. Season to taste with salt and yeast. Place the leaves between two silicone baking mats on a baking sheet and bake for 5 minutes. Remove the top mat and bake for another 5 minutes. Turn the leaves over, rotate the pan, and bake again for 5 minutes. Continue to turn and bake until crispy, 2 to 3 rotations. Store in a dry box.
Heat the grapeseed oil for deep-frying to 350°F (175°C).
Using 2 spoons, thickly coat the chilled Beignet Centers in the Beignet Batter and fry in the grapeseed in small batches for a few minutes, turning and basting with oil, until golden brown. Drain on paper towels, snip off any tails of batter with scissors, then roll the hot beignets in a little of the malt vinegar powder. Arrange the beignets on serving plates, grate cheese over the beignets, garnish with Kale Chips, and serve immediately.