Cabernet-Balsamic Burgers with Sautéed Mushrooms & Onions

INGREDIENTS

5 tsp

olive oil, divided

4 cups

thinly sliced red onion

1 1/2 tsp

chopped fresh thyme

1/2 cup

cabernet sauvignon or other dry red wine

2 tbsp

balsamic vinegar

3/4 tsp

salt, divided

1 8 ounce package

sliced mushrooms

1 1/2 lb

ground sirloin

Cooking spray

1/3 cup

light mayonnaise

1 oz

blue cheese, crumbled (about 1/4 cup)

garlic clove, minced

whole-wheat hamburger buns

1 1/2 cups

baby arugula