For chicken: Arrange chicken in single layer in baking dish. Sprinkle with garlic and cayenne. Pour beer over. Marinate at room temperature 2 hours, turning once.
Pour marinade into heavy large skillet and bring to a simmer. Add chicken, cover and cook until tender, about 10 minutes. Drain chicken and cool slightly; cube or shred.
For sauce: Mix flour, cumin, salt, pepper, coriander and cayenne. Melt butter in heavy large saucepan over medium-low heat. Whisk in flour mixture and stir 3 minutes. Gradually whisk in milk and cream and stir until sauce thickens, about 10 minutes. Blend 1 cup sauce into eggs. Whisk mixture back into sauce and cook for 1 minute, do not boil. Adjust seasoning.
For Filling: Combine chicken, olives, chilies, cheeses and onion in large bowl.
To assemble: Preheat oven to 350 degrees. Heat tortillas in nonstick skillet until soft and hot. Spread 1/2 cup sauce in bottom of 5-6 cup round, deep baking dish (souffle dish works well). Top with tortilla. Spread with about 2 tablespoons sauce. Cover evenly with layer of filling. Top with tortilla. Repeat layering with remaining ingredients. Pour any remaining sauce over top. Bake until heated through, about 30 minutes. Cool 5 minutes. Cut into wedges to serve. Pass bowls of sour cream and salsa separately.