Put whole wheat flour, salt, sugar, and dry yeast into a bowl.
Pour in warm water and milk, then knead the dough.
Once the dough comes together, add butter and knead until smooth.
Chop the walnuts and mix them into the dough.
Let the dough rise for about 1 hour.
Shape the dough and place it into a loaf pan.
Let the dough rise again in the pan for 30–40 minutes (second proof).
Bake in a preheated oven at 180°C for 30–35 minutes.
Cool the bread on a wire rack.