Cut 12 squares of parchment paper about the size of your palm. Arrange them on a baking sheet and lightly spray or grease each square. Set aside.
Make the glaze: in a medium bowl whisk together 1 1/2 cups powdered sugar and 2–3 tablespoons milk until smooth and lump-free. The glaze should be thick but pourable; add the third tablespoon of milk for a thinner, more translucent glaze if desired. Set aside.
In a medium saucepan over medium heat combine 1 cup hot water, 6 tablespoons (85 g) unsalted butter (cut into cubes), 1 tablespoon granulated sugar, and a pinch of salt. Stir until the butter is fully melted and the mixture comes to a boil.
Remove the pan from the heat and immediately add 1 cup all-purpose flour all at once. Stir quickly and vigorously with a wooden spoon until the dough forms a smooth ball and pulls away from the sides of the pan.
Return the pan to medium heat and cook the dough, stirring continuously, for 2 minutes to dry it out slightly.
Transfer the dough to the bowl of a stand mixer fitted with the paddle attachment. Mix on medium–high for 1 minute to cool the dough slightly.
Reduce the mixer speed to medium. Add the 3 large eggs one at a time, mixing fully after each addition. Then add the 2 egg whites and mix until the batter is smooth, glossy, and holds its shape well for piping.
Fit a large pastry bag with a large star tip, fill it with the batter, and pipe donut rings onto the prepared parchment squares on the baking sheet.
Pour 2–3 inches of vegetable oil into a heavy-bottomed saucepan and heat to 370°F (use a thermometer). Once the oil reaches 370°F, reduce the heat slightly and maintain the oil between about 350–370°F while frying.
Fry the donuts in batches: using a spatula, gently lower a donut (parchment side up) into the oil. After a few seconds the parchment will loosen—use chopsticks to peel off and discard the parchment. Fry the donut about 1 minute per side, or until puffed and golden brown. Do not overcrowd the pan.
Remove each donut with a slotted spoon and place on a cooling rack set over a sheet pan to drain. While still hot, spoon or dip the top of each donut into the prepared glaze so it adheres.
Repeat frying and glazing with the remaining donuts. Let the glaze set for about 30 minutes before serving.