In your mixer, with your paddles, add the yeast, milk and 2 C flour and mix until smooth.
Then let it rest, covered, in a warm spot for 20 mins.
Mix to deflate and switch over to a dough hook.
Add the sugar, salt, vanilla, eggs and egg yolks and mix on low until smooth!
Now your'll start adding the flour, 1/2 cup at a time.
Keep adding flour and mixing on low until the dough pulls away from the sides. It will still be very moist, and a little sticky, but not too much.
Cover the dough and refrigerate for at least 1 hour, up to 12.
Pull the dough out and place on a lightly floured surface. Flour the top and roll out the dough...
Roll it out 1/2 inch thick.
Take a 3 inch circle cutter and dip it in flour before each cut.
Press the cutter all the way down, the twist a bit, then pull up.
Place the donuts on the plastic wrap sprayed with non stick spray (like I talk about in this video to keep your dough from sticking), make sure there is space between each one.
Spray some more plastic and cover the donuts, let them proof/rise for 5-20 mins
Start heating 2 inches of oil over medium/high.
You want the oil to be at 360 degrees, for me I maintained 360 between medium and medium/high. It's a little tricky, just keep the thermometer in to keep an eye on it.
Check the dough every 5 mins by pressing a finger into the dough and if it springs back fast it needs more time, springs back slowly and it's ready!
Fry for 1-2 mins on each side. For me 1 1/2 mins on each side was perfect!
Flip to the second side carefully, you don't want to splash hot oil everywhere, I used a wide slotted flipper.
Pull out and let drain on a wire rack over paper towels (I like to do it in a jelly roll pan to keep the grease contained.
Let them cool completely
Roll in powdered sugar on both sides
Then using a bismark tip in a piping bag filled with your favorite jelly
Poke a hole in one side, wiggle the long tip back and forth then squeeze filling with jelly, then repeat on the opposite side to make sure the donuts are filled completely.