In a mixer bowl, combine flour, yeast, and sugar. Attach the dough hook. Warm the milk and butter slightly in the microwave until lukewarm. Gradually pour the milk and butter into the mixer bowl. Add eggs, vanilla, and finally the salt while kneading. Continue kneading for at least 5 minutes until the dough is smooth but sticky. Transfer the dough to a greased bowl (use oiled or floured hands). Cover with plastic wrap and let it rise for 1 hour at room temperature, then refrigerate for 1 hour or overnight.

Deflate the dough, place it on a floured surface, and divide it into 2.12-ounce/60-gram portions. Roll into balls, placing the seam side down. Place each ball on a square of parchment paper or floured surface. Lightly oil the dough balls with cooking spray or brush with canola oil to prevent drying. Cover with a towel and let rise until doubled in size.

Heat oil to 320–340°F (160–170°C). Test with a wooden spoon or a small dough piece for bubbles.

Gently place the dough balls in the oil, parchment side up. Remove the parchment after a few seconds. Fry each side for 2 minutes until golden. Avoid burning or undercooking. Transfer to paper towels. Poke a hole in each donut and fill with jam or your choice of spread while still warm. Dust with powdered sugar and serve.