In a small bowl, combine the yeast, milk, and 2 Tbsp of the sugar. Mix well and leave to sit for 10-15 minutes, or until foamy.

In the bowl of a stand mixer fitted with the dough hook, combine the flour, salt, and remaining 2 Tbsp sugar. Mix briefly to combine. Add the eggs, vanilla, and foamy yeast mixture to the bowl. Mix on low for 2-3 minutes, until the dough starts to come together. Increase the mixer speed to medium and mix for another 10 minutes, until the dough is soft and smooth.

Reduce mixer speed to low, and slowly add the butter, waiting until fully incorporated before adding more. This should take 3-4 minutes. Once incorporated, increase speed to medium and mix for 5 more minutes.

Transfer to an oiled bowl, cover tightly with plastic wrap, and place overnight in the fridge to rise.

Line two sheet pans with parchment paper and turn the dough out onto a floured surface. Roll until 1/2” thick.

Cut out circles of dough and use a small cutter to cut holes in the middle. Place on parchment squares, cover lightly with plastic wrap, and allow to rise for 45-50 minutes.

Heat oil to 350°F in a large pot or deep fryer. Combine cinnamon sugar in a bowl.

Test oil temperature with dough scraps. Fry doughnuts until golden brown, about 3-4 minutes, flipping occasionally. Transfer to a cooling rack and toss in cinnamon sugar.

Enjoy fresh, or store in an airtight container.