01 -
Heat oil in large skillet over medium-low heat. Add sliced onions with pinch of salt, cook 25-30 minutes stirring occasionally until golden brown and fragrant.
02 -
Mix ground beef, breadcrumbs, egg, garlic, salt and pepper in bowl. Don't overmix. Roll into 16-18 golf ball-sized meatballs.
03 -
Remove half the onions, set aside. Increase heat to medium-high, brown meatballs on all sides, about 2-3 minutes per side.
04 -
Return reserved onions to pan with broth, Worcestershire, and thyme. Simmer, cover, cook 15 minutes until meatballs are cooked through.
05 -
Sprinkle Gruyère over everything, cover 2-3 minutes until melted and bubbly.
06 -
Sprinkle with fresh parsley and serve immediately from the pan with crusty bread.