Preparation Time : 15 mins
Cook Time: 25 mins
Servings: 4
|
2 handfuls of lettuce |
|
1 onion |
|
4 large white button mushrooms |
|
1 tbs olive oil |
|
500 g beef mince |
|
4 slices of cheese |
|
salt, pepper, onion powder |
|
mustard |
|
4 hamburger buns |