1. Beat the flour with salt.
2. In a small bowl, whisk together the warm milk, sugar, egg, and dry yeast.
3. Pour liquids into the dry ingredients and knead until a soft dough forms.
4. Form the dough into a ball, cover and let it rise for 2 hours.
5. Cut the dough into portions and roll each one into a ball. Let it rise for 20 minutes.
6. Roll out each ball into a rectangle with rounded edges and place a small portion of hazelnut paste in the middle, using a pastry bag. Pinch both edges of the dough, then connect both ends of the dough to form a circle-shaped donut. Set aside for 20 minutes.
7. Cook donuts in preheated oil for 4 minutes (each side) or until golden brown and cooked through.
8. Top each donut with sugar.
