In the bowl of a stand mixer or a large mixing bowl, combine the warm water, yeast, and 1 tablespoon of sugar. Let the mixture sit until foamy, around 5 minutes. If it doesn’t foam, the yeast is inactive and should be replaced.

Add the remaining ½ cup sugar, shortening, egg yolks, and vanilla to the foamed yeast. Mix using the paddle attachment until the shortening is dispersed but not fully incorporated.

Sprinkle in 1 cup of the flour, followed by the salt and baking powder. Lightly stir the dry ingredients into the flour before incorporating them into the dough. Beat for 1 minute until fully integrated.

Continue adding the remaining flour, 1 cup at a time. Switch to the dough hook or knead by hand once the mixture becomes too thick. Knead for about 5 minutes until the dough is smooth and pulls away from the bowl. A slightly sticky dough is preferred for a tender result—only add additional flour if absolutely necessary.

Bring at least 2 quarts of water to a boil in a large pot. Lightly flour a baking sheet (avoid silicone mats). Shape the kneaded dough into a ball, transfer it to the sheet, then flatten it into a 6x6 inch square. Lightly dust the top with flour and cover with a cloth.

Warm the oven by turning it on to 350°F for 30 seconds, then switch it off. Place the dough inside the oven on a rack above a 9x13 inch pan filled with the boiling water. Allow it to rise in this humid environment for 1 hour until doubled.

Once risen, remove the dough and transfer it gently onto a floured surface. Use a rolling pin to flatten into an 11x12 inch rectangle. Slice the dough into four quarters, then divide each quarter into three long rectangles to yield 12 donuts. Trim edges for uniformity if desired.

Transfer the shaped dough to two floured baking sheets, spacing each piece at least 2 inches apart. Reheat the oven as before and repeat the steam method using boiling water in a 9x13 inch pan. Let the dough rise again for 45 minutes or until doubled.

Fifteen minutes before the second rise ends, heat about 2 inches of peanut oil in a deep, heavy pot to 350°F, monitoring with a candy thermometer.

Carefully lower 2–3 dough pieces at a time into the hot oil using a spatula or scraper. Fry each side until golden, approximately 30–40 seconds on the first side and 20 seconds on the other. Transfer to paper towels to drain and let cool completely before glazing.

In a mixing bowl, whisk together the powdered sugar, corn syrup, salt, vanilla, maple extract, and hot water. Adjust consistency with additional sugar or water as needed. The glaze should be thin enough for dipping but not runny.

Dip the smooth side of each cooled donut into the glaze and allow excess to drip off. Place on a wire rack to set for 15–20 minutes before serving.