Melt butter at medium heat. Combine both types of flour, yeast, milk and water. Add butter and salt and knead until you've got a smooth dough. Let the dough rest covered with a kitchen towel for approx. 2 hours at room temperature.
Preheat the oven to 190 °C. Divide the dough into 4 pieces and shape into burger buns. Brush with milk and sprinkle with sesame seeds. Bake for 20 minutes until golden.
For the burger:
In the meantime, knead ground beef and egg together and season with salt and pepper. Shape into 4 burger patties and fry them in sunflower oil.
Let the buns cool down for a minute, then cut open and add ketchup or sauce of your choice. Add lettuce, beef patty, cheese and tomato slices and close.
Tipps
Try homemade fries or oven-baked fries (sweet potato fries are my favorite) as side dish!