Green Chile Enchiladas

1/3 cup butter
1/3 cup flour
2 1/2 cups half and half
1 (7 oz) can green chiles
1/2 cup onion, minced
1/8 tsp cayenne
1 medium onion, minced
4 cups cheddar cheese, grated
4 cups jack cheese, grated
oil for frying
12 corn tortillas
2 cups sour cream
Melt butter in small saucepan and sprinkle in flour. When flour is slightly browned and begins to bubble, slowly stir in half and half. Simmer, stirring regularly for 5 minutes. Add chiles, 1/2 cup minced onion and cayenne, and simmer 10 minutes. Mix cheeses with remaining minced onion. Dip each tortilla into hot oil for 5 seconds and drain on paper towel. Scoop cheese mixture onto each tortilla, roll up and place in baking pan. Top with green chile sauce, sprinkle on remaining cheese and broil until bubbly. Garnish generously with sour cream.