Instructions

1. First, make the donuts. In a stand mixer fitted with the paddle attachment, combine 2 cups of the flour with the granulated sugar, yeast, and salt on low speed until combined.
2. In a microwave-safe bowl, microwave the milk and butter until the mixture is warm to the touch and the butter is mostly melted, about 45 seconds (you don’t want the mixture to be steaming or too hot, as this can kill the yeast).
3.  Pour the milk mixture into the flour mixture, along with the egg yolks. Beat everything together on low speed, gradually increasing to medium speed, for 2 minutes. The dough will look more like batter, but this is correct! This step kicks off the gluten development. 
4. After 2 minutes, change to the dough hook attachment. Add in an additional 1 ¼ cups of flour and knead on low speed until combined and a soft dough forms. Use a silicone spatula to scrape down the sides of the bowl. Knead on low speed, stopping the mixer occasionally to re-disperse dough, until the dough starts to pull away from the sides of the bowl and forms a ball around the dough hook, about 3 minutes. Increase to medium-low speed and knead until the dough becomes smooth and supple, about 5 minutes. If the dough feels too wet, add in the additional ½ cup flour and mix for an additional minute or so.
5. Turn the dough onto a clean, lightly floured surface, cover loosely with a dish towel, and let rest for 10 minutes. 
6. Use a rolling pin to roll the dough out to a 12-inch circle about ½ inch thickness. Use a 3-inch round cookie cutter to cut out as many donuts as possible. Gather the scraps together into a ball and gently knead them back together. Let the dough rest for 15 minutes, then roll out the scraps and cut the dough again–you should end up with 10 donuts.
7. Place the donuts 3 inches apart on lightly greased or parchment lined baking sheets. Cover the baking sheets loosely with a dish towel or plastic wrap. Let rise in a warm place until the donuts have doubled in size, about 1 hour.
8. Heat 4 inches of oil in a large pot over medium-low heat to 350°F. Place a cooling rack on top of a baking sheet and set aside. 
9. While the oil heats up, prepare your filling and coating. Place 1 cup of granulated sugar in a medium sized bowl and set aside. Place the strawberry jam into a piping bag fitted with a metal tip with a ½-inch tip. Set aside.
10. Fry 2 to 3 donuts at a time (being careful to not overcrowd the pot) for 2 minutes on each side. You’ll know to flip the donuts over when they float to the top of the oil and are golden brown around the bottom edge right where it meets the oil. Use a slotted metal spatula to transfer them to the prepared cooling rack and repeat with the remaining donuts.
11. Once the donuts are cool enough to the touch (but still warm), toss in the granulated sugar. Insert the piping bag tip into the side of each donut and firmly squeeze a few tablespoons of jam into the center of the donut. Serve within 4 hours of frying (but they’re best while still warm, obviously).