Hamburger Steak with Onion & Mushroom Gravy

INGREDIENTS

1 lb

Ground sirloin

4 cloves

Garlic

1

Mashed potatoes

1 cup

Mushrooms

1

White onion, large

1 1/2 cups

Beef stock, low-sodium

1 tbsp

All-purpose flour

1

Kosher salt and freshly ground pepper

2 tsp

Olive oil, extra-virgin

1 tsp

Red wine vinegar

1 tsp

Butter