Sprinkle the shrimp evenly with salt and pepper and set aside.
Place the dried chilis in a medium bowl and cover with boiling water. Steep chilis in the hot water until softened, about 20 minutes.
Puree softened chilis and ½ cup of the steeping liquid in a food processor or blender until smooth and set aside.
Heat a large, deep skillet over medium-high heat and add olive oil to the pan. Stir in garlic and warm until fragrant, about 15 seconds, being careful not to burn.
Add shrimp to the pan, without over crowding, and heat for 90 seconds per side. The minute the shrimp turns pink, it is cooked so be careful not to over cook. It shouldn't take more than 3-4 minutes total. Remove cooked shrimp from the pan and set aside.
Stir the tequila into the hot skillet and use a wooden spoon to deglaze any browned bits from the bottom of the pan.
Return the cooked shrimp along with the pureed chilis and lime juice to the pan. Bring to a simmer then reduce to low and heat for 4-5 minutes or until warmed through.
Right before serving, finish the shrimp with butter and stir until melted through. Check for seasoning and add more salt or pepper to taste.
Serve with warmed tortillas, rice or tossed into pasta if you wish.