Prepare the Dough:In a large mixing bowl, combine the warm whole milk and instant yeast. Let it sit for about 5 minutes until the yeast is activated and bubbly. Add the granulated sugar, salt, and egg to the mixture, stirring well to combine. Gradually add the all-purpose flour, 1 cup at a time, mixing until a dough forms.
Knead the Dough:Turn the dough onto a floured surface and knead it for about 8-10 minutes until it becomes smooth and elastic
Make the Filling:While the dough is rising, prepare the cinnamon filling. In a small bowl, melt the unsalted butter, then mix in the brown sugar and cinnamon until smooth and combined. Set aside.
Roll Out the Dough:Once the dough has risen, punch it down to release the air. Turn it out onto a floured surface and roll it into a rectangle, about 1/4-inch thick. Spread the cinnamon-brown sugar filling evenly over the entire dough.
Shape the Donuts:Carefully roll up the dough into a tight log, then cut it into 1-inchthick slices. Use a donut cutter or your hands to shape each piece into a rounddonut, making sure the hole in the center is large enough to fry properly
Fry the Donuts:Heat vegetable oil in a deep frying pan or large pot to 350°F (175°C). Carefully drop the donut slices into the hot oil, a few at a time, and fry for 2-3 minutes on each side, or until golden brown. Remove the donuts from the oil and place them on a paper towel
Prepare the Icing:In a medium bowl, whisk together the powdered sugar, whole milk, and vanilla extract until smooth and creamy.
Glaze the Donuts:Once the donuts have cooled slightly, dip each one into the icing,ensuring the top is fully coated