Make the dough: In the bottom of a large mixing bowl, combine the yeast, sugar and milk. Let stand for 5 minutes; it should become a little foamy. Whisk in yolks, any zest or extracts youd like to use, then butter and zest. Dont worry if the butter doesnt fully combine.

With a stand mixer: Add half the flour and let the dough hook mix it in slowly, on a low speed. Add second half of flour and salt and let the dough hook bring it together into a rough dough. Run machine for 3 to 4 minutes, letting it knead the dough into a smooth, cohesive mass.

Cover with plastic wrap and let rest at room temperature for 1 hour, or in the fridge overnight.

On a lightly floured counter, roll dough to a 1/2-inch thickness. Cut into 2-inch rounds; no need to re-roll scraps unless you wish; I like to keep the odd shapes for getting the hang of frying before cooking the final doughnuts. Or, if youre vehemently against scraps and re-rolling, you can make small square doughnuts, which are surprisingly cute. Let cut dough rise for another 30 minutes at room temperature, loosely covered with a towel at room temperature, or in the fridge overnight, on an oiled tray, covered loosely with oiled plastic wrap (use this longer rise only if did the 1-hour rise the first time; two overnights is too much for this dough).

Fry the doughnuts: Heat 2 inches of oil to 350°F (175°C) in a cast-iron frying pan (I like using one because it so delightfully re-seasons them) or heavy pot. Use your dough scraps to practice and get an idea of how quickly the doughnuts will cook. Then add about 4 doughnuts at a time to the oil, cooking on the first side until golden brown underneath, about 1 to 2 minutes, but often less so keep a close eye on them. Flip doughnuts and cook on the other side, until it, too, is golden brown underneath, about another minute. Drain doughnuts, then spread them on a paper towel-lined plate to absorb extra oil. Repeat with remaining doughnuts.

When doughnuts are cool enough to handle, place jelly or jam in a piping bag with a round tip with a 1/4- to 1/2-inch opening. You can fill doughnuts from the tops or sides; I did half with each. Press the tip of the jam bag halfway into the doughnut, and squeeze in the jam until it dollops out a little from the hole. Repeat with remaining doughnuts.

Finish doughnuts: Either generously shower doughnuts with powdered sugar on either side, shaken from a fine-mesh strainer, or roll the doughnuts gently in a bowl of powdered sugar.