Start by preparing the tangzhong so it has time to cool. In a small saucepan over medium-low heat, whisk together the flour and milk, until smooth. Continue to cook the mixture over medium-low heat, whisking constantly, until the tangzhong thickens and the whisk leaves a line as you whisk. It should look almost gluey! If you have a thermometer here, I do recommend using it, the tangzhong should reach 150F.

Remove from the heat, transfer the tangzhong to a small bowl, and set aside to cool to room temperature.

Activate the yeast first. Pour the warm milk into a small bowl or glass measuring cup. Add 1 tbsp (12g) of the granulated sugar and sprinkle the yeast overtop. Stir and allow to sit for 5-7 minutes, until frothy and activated.

In a large bowl, whisk together the flour and salt. Set aside.

Once activated, pour the yeast mixture into the bowl of a stand mixer (or a large bowl if mixing/kneading the dough by hand). Add the rest of the sugar (¼ cup minus the 1 tbsp that was used to activate the yeast), all of the tangzhong that was previously prepared, Greek yogurt or sour cream, very softened butter, eggs, vanilla, and the flour mixture.

With the dough hook attachment (or with a wooden spoon if mixing by hand), mix on low speed for 1 minute, until barely combined. Allow to rest for 5 minutes so the flour can soak up the liquids.

Then, mix on medium speed for 5-7 minutes, until the dough is elastic, smooth, and is pulling away from the sides of the bowl. If the dough seems a little too sticky, you can add 1 tbsp more flour at a time, until it starts to pull away from the sides of the bowl.

Transfer the dough to a lightly oiled bowl. Cover and allow to rise in a warm environment for 1-1.5 hours, or until doubled in size.

Once the dough is almost finished rising, cut out 10-12 squares of parchment paper and spread them across 2 baking sheets.

Once the dough is doubled, punch it down and turn it onto a lightly floured surface. Roll the dough out to ~½” thickness. Using a 3” donut cutter, cut the donuts out. Then, using a smaller 1” cutter, cut out little holes in the middle of each donut.

Place the donuts onto the prepared parchment paper squares on the baking sheets. Loosely cover with a kitchen towel and allow to proof for 30-45 minutes, until puffy.

Prepare the cinnamon sugar by mixing together the sugar and cinnamon in a medium bowl.

When the donuts are almost done proofing, fill a large, heavy-bottomed pot or Dutch oven with oil, filling ~2” in the pan. Heat on medium-high until it reaches 350F-365F.

Line a wire cooling rack with a thick layer of paper towels.

Once the oil is hot enough, carefully transfer the parchment paper squares with the donuts on them slowly into the hot oil, 2-3 at a time. Fry the donuts for 1-2 minutes on each side (2-4 minutes total), until golden brown.

Using a slotted spoon, carefully remove the donuts from the oil and to the rack with paper towels. Repeat with the remaining donuts.

While the other donuts are frying, dip the warm donuts into the cinnamon sugar mixture, making sure to roll and coat both sides. Then place onto a cooling rack or piece of parchment paper.

Serve warm with a cup of coffee.