Combine 2 1/2 teaspoons active dry yeast, 1 tablespoon sugar and 1/2 cup warm water in the bowl of a freestanding electric mixer. Whisk together until the yeast is dissolved, and then set the bowl aside for 5 minutes to let the sugar and yeast start working together.
In a medium bowl, combine together 2 1/4 cups bread flour, 1/2 cup nonfat milk powder and 1 teaspoon kosher salt. Set aside. In the bowl of a liquid measuring cup, gently whisk together 2 large eggs, 1 teaspoon vanilla extract and 1 teaspoon white vinegar until homogenous. Set aside.
Fix the freestanding electric mixer with a dough hook and add half the dry ingredients to the yeast and water in the mixer bowl. Mix on the mixer's slowest setting for a minute or two, just until the ingredients have started to come together. Add half the wet ingredients before mixing for another minute or two, just until they've started to be absorbed into the dough. Repeat with the remaining dry, then wet ingredients. Finally, add 1 tablespoon unsalted butter into the dough. The dough will be almost rebelliously wet — wetter than your average brioche dough — and that's the way you want it. Continue mixing for another 8 minutes on speed 1 until the dough is smooth. Once the dough is smooth, transfer to a lightly greased medium bowl, cover with a flour cloth and place in a warm, draft-free, dark spot (like an off oven) for 2 hours.
After 2 hours, turn the dough out into your lightly floured work space. With clean, slightly wet hands, pinch off golf-ball sized pieces of wet dough with your first finger and thumb. Smooth out each dough ball in your hands or in the counter, creating a ball shape by grabbing one side of the dough and then folding it over the top to the other side of the dough. Be sure to stretch each dough segment only to the point of resistance, before folding them across the entire length of the dough mass. Transfer to a greased baking sheet, leaving about 2 inches between each ball. When all the dough has been balled, spray with a faint mist of cooking spray and cover loosely with plastic wrap, before leaving out on the counter to rise for another 2 hours.
After the dough has risen for another 2 hours, pull out your deep-fryer or a heavy bottomed pan like a Dutch oven or cast iron skillet. Heat around 4 to 6 cups of vegetable oil to 400 (F). While the oil is warming up, make the cinnamon sugar topping: in a medium bowl, combine 1 cup granulated sugar, 1/4 cup light brown sugar, 1 tablespoon ground cinnamon and 1 teaspoon kosher salt. Whisk together until well combined, before setting aside.
Once the oil is ready, use a perforated spoon to gently pick up a proofed dough ball and slowly lower it into the hot oil. Submerge and flip the dough as it slowly browns. At 400 (F), the dough balls should take 1-2 minutes to fry all the way through.
Use the same perforated spoon to pull the malasadas out of the oil. Transfer to a wire rack lined with paper towels to soak up any excess grease. Allow the malasadas to cool and drain for a minute, then, while they're still hot, transfer them one by one into the bowl of cinnamon sugar and toss until completely coated. Allow the malasadas to rest for a few more minutes before serving/eating — if you rush this, the malasadas will be doughy and underdone in the center. But be sure to eat while warm since they are best on the day they are made.