In a shallow bowl, whisk eggs and buttermilk. Mix bread crumbs and taco seasoning in a separate shallow bowl. Dip ravioli in egg mixture, then in crumb mixture, patting to help coating adhere.
In an electric or deep skillet, heat 1/2 in. of oil to 375°. Fry ravioli, a few at a time, 1-2 minutes on each side or until golden brown. Drain on paper towels; immediately sprinkle with cheese. For sauce, in a small saucepan, heat enchilada sauce. Stir in sour cream until blended; heat through. Serve with ravioli and, if desired, jalapeno slices.