Heat the milk a little, dissolve the yeast in it, add sugar, soft butter, salt, beaten egg and flour. Knead not too thick dough. Put it in a warm place for 1 hour, then knead it with your hands. Divide the finished dough into small pieces, they should be in pairs.
Roll the pieces a bit.
In the middle of the test, put the filling, it can be boiled condensed milk, slices of bananas, apples or any jam. Cover with a second piece of dough and cut with a glass, so the edges are well glued.
Heat a large amount of oil in deep fat or just in a pan, dip the finished donuts in boiling oil and cook on both sides until golden brown.
Place donuts on paper towels to remove excess fat. Let cool slightly and serve.
Donuts with filling are very tasty, tender and airy, the filling can be the most varied. Such donuts can be sprinkled with powdered sugar before serving, the dough tastes more neutral, it is not sweet and not salty. The filling may also be not sweet, for example pieces of boiled chicken, grated cheese or cottage cheese. Donuts are great for the whole family for breakfast or as a complement to first courses.