Servings: 8

¼ cup butter, melted, plus 1 tablespoon butter, separated ¼ cup butter, melted, plus 1 tablespoon butter, separated
½ onion, chopped, about ½ cup ½ onion, chopped, about ½ cup
¼ cup flour ¼ cup flour
2 cups milk 2 cups milk
2 cups chicken stock 2 cups chicken stock
1 ½ cups coarsely chopped broccoli florets 1 ½ cups coarsely chopped broccoli florets
1 cup matchstick-cut carrots 1 cup matchstick-cut carrots
1 stalk celery, thinly sliced 1 stalk celery, thinly sliced
2 ½ cups shredded sharp cheddar cheese (6 oz.) 2 ½ cups shredded sharp cheddar cheese (6 oz.)
salt and ground black pepper to taste salt and ground black pepper to taste

Melt 1 tablespoon butter in a skillet over medium-high heat. Saute onion in hot butter until translucent, about 5 minutes. Set aside.
In Instant Pot, whisk ¼ cup melted butter and flour together over medium-low heat; cook until flour loses its granular texture, adding 1 to 2 tablespoons of milk if necessary to keep the flour from burning, 3 to 4 minutes.
Gradually pour milk into the flour mixture while whisking constantly. Stir chicken stock into milk mixture. Bring to a simmer; cook until flour taste is gone and the mixture is thickened (about 20 minutes). Add broccoli, carrots, sauteed onion, and celery; simmer until vegetables are tender, about 20 minutes. Season with salt and pepper to taste. I used Slow cook - medium and let it sit for 1 to 2 hours before adding cheese.
Stir Cheddar cheese into vegetable mixture until cheese melts. Season with salt and pepper to taste.