To get extra crispy fried shrimp you can deep fry them. Marinate the shrimp in one cup of buttermilk. Meanwhile, add 6 cups of vegetable oil to a large Dutch oven and heat over medium-high heat for 20 minutes. Coat the shrimp in cornstarch, shake excess off, then add shrimp to oil. Stir to separate shrimp and fry for 4-5 minutes until golden brown. Work in batches, coat crispy shrimp in sauce, and assemble tacos.