Put lukewarm water in a mixing bowl along with yeast, sugar, salt, and oil and stir until the yeast is dissolved.

Add sifted flour and oatmeal and mix everything well together.

Add wheat flour a little at a time until the dough releases from the bowl and is smooth, without sticking to your fingers.

Let the dough rise in a flour-dusted bowl covered with a shower cap for 30 minutes.

Turn the dough out onto a floured surface, divide it into 15 pieces. Roll into buns and place them close together on a baking sheet lined with baking paper and let them rise again for 30 minutes.

Brush the buns with egg yolk and bake for 30 minutes at 220 degrees Celsius (428 degrees Fahrenheit) with convection.