In same saucepan melt the 3 tablespoons butter. Blend in flour, coriander and salt. Stir in chicken broth all at once; cook and stir until thickened and bubbly. Remove from heat; stir in sour cream and 1/2 cup of cheese. Stir 1/2 cup of the sauce into the chicken. Dip each tortilla into remaining hot sauce to soften; fill each with about 1/4 cup of the chicken mixture. Roll up. Arrange rolls in a 13"x9"x2" baking dish; pour remaining sauce over. Sprinkle with remaining cheese. Bake, uncovered in 350 degree oven about 25 minutes or until bubbly. Serves 6.