White Chicken Chili

2 cans (1/2 pound) navy beans
1 large onion chopped
1 stick unsalted butter
1/4 cup all-purpose flour
3/4 cup chicken broth
2 cups half-and-half
1 teaspoon Tabasco, or to taste
1 1/2 teaspoons chili powder
1 teaspoon ground cumin
1/2 teaspoon salt, or to taste
1/2 teaspoon white pepper, or to taste
2 4-ounce cans chopped mild green chilies
2 pounds boneless, skinless chicken cooked and chopped
1 1/2 cups grated Monterey Jack Cheese
1/2 cup sour cream

In a skillet, cook onion in 2 tablespoons butter over moderately low heat; remove onions. Add 6 tablespoons butter and whisk in flour. Cook, whisking constantly, 3 minutes. Stir in onion and gradually add broth and half-and-haldf whisking constantly. Bring to a boil then simmer for minutes. Add remaining ingredients except for sour cream. Cook over moderately low heat, 20 minutes; then add sour cream. Serve with salsa.