Add enough vegetable oil in a dutch oven or heavy bottomed deep pan for the oil to be 3 inches deep. Heat to 375 degrees over medium heat using a candy thermometer. You can also use a deep fat fryer if you have one.
In a large stand mixer bowl, add in 4 cups of flour, butter, sugar, eggs, soured milk, vanilla, almond extract, nutmeg, baking powder, and baking soda. Mix on low with the paddle attachment until well combined.
Stir in as much flour as needed to make the dough easy to handle. I added about an additional four cups to mine.
Knead on a clean, floured counter top for about 2 minutes. Keep the counter top well floured. Roll dough out to ⅜ inch thickness. Flour a donut cutter, and cut out donuts.
Carefully place dough into the hot oil. Fry on each side until golden brown, about 2-3 minutes. It's very important to keep your oil at 375. If it's too hot, the inside will be raw and the outside will be done. If it's too cold, the dough will be super oily.
Flip the dough and fry on the other side for 2 - 3 minutes.
Using tongs or a slotted utensil, remove donuts from the hot oil and place on a paper towel lined plate to cool. If you want to cover with sugar, do it while the donuts are hot.
Repeat with the rest of the donuts.
Soured milk is 1 cup of milk and 1 tablespoon of vinegar. Let it sit for 5 - 7 minutes. This recipe was adapted from Land O' Lakes.