Salsa Green Beans without jalapeno

4 tablespoons butter 1 yellow onion , finely chopped 4 tablespoons all-purpose flour 2 cups heavy cream 1 teaspoon salt 1/2 teaspoon pepper 1 (28 ounce) can[...]

1 lb tomatillo, husks removed and rinsed 3 serrano chilies , finely chopped 1/2 cup cilantro , roughly chopped and loosely packed 2 tablespoons cilantro ,[...]