Broccoli Cheese Soup

I got this from a blog a long time ago but I think the original is on AllRecipes somewhere. Anyhoo, here's our favorite version:

2 Tablespoons butter
3 cups chicken broth
1/2 large yellow or white onion, finely chopped
1/3 cup all-purpose flour
1 crushed garlic clove
1 1/4 cups 2% milk
1/2 teaspoon freshly ground pepper
5 oz grated sharp cheddar
Large handful of grated monterey jack cheese
16 oz package frozen chopped broccoli
1. Melt butter in stock pot on medium, add onion and cook til' soft. Add pepper and garlic, and cook for a few minutes. Add broccoli and chicken broth. Bring to a boil, then simmer to broccoli is tender (10-15 minutes).
2. In separate bowl, whisk flour into milk until completely dissolved. Stir into soup, stirring frequently ti'l thickened. Reduce heat to low, and then stir in cheese til smooth and heated through. Salt to taste.
Serves 4-5.