This is adapted from CD Kitchen. I make a lot of it and then freeze it in single-serving packets.
1/2 medium onion, chopped
1/4 cup melted butter
1/4 cup flour
2 cups 2% milk
2 cups chicken stock or bouillon
1/2 pound fresh broccoli
salt and pepper to taste
1/4 tsp cayenne pepper
8 ounces grated sharp cheddar
Saute onion in butter. Set aside with broccoli.
Cook melted butter and flour using a whisk over medium heat for 3-5 minutes. Stir constantly and slowly add hot chicken stock whisking all the time.
Put everything together. Add milk, salt, pepper, and cayenne. Puree, return to stove until hot, then serve.