Food Network teaches how to crush, slice and mince garlic. Peel off some of the papery skin from the garlic and then smash the head of garlic with the heel of your hand to loosen the cloves; if you only need a few cloves, leave the head intact and pull some off. Separate the cloves. To peel a clove, cut away the root end with your knife. Lay the flat side of the knife over the clove while holding the knife handle, then with the heel of your free hand carefully whack the knife against the garlic to separate the skin from the clove. To crush the peeled garlic, lay the flat side of the knife over the clove and smash it again. To slice peeled garlic, lay the clove flat on the cutting board and hold it with the fingertips of one hand, keeping them curled under. Using a rocking motion with the knife, make thin slices by moving the knife slowly across the clove. To mince peeled garlic, lay the flat side of a knife over the clove and smash it. Roughly chop the clove then move your free hand flat across the tip of the knife and use a rocking motion to chop the garlic until it’s finely minced.
Whisk together 1/4 cup of the oil, 2 tablespoons of the thyme, ancho powder and chopped garlic in a small bowl. Skewer the shrimp and brush with marinade.
Place the remaining 1/2 cup of the oil in a small saucepan, add the sliced garlic and cook until the sliced garlic is lightly golden brown. Remove the garlic slices with a slotted spoon to a plate lined with paper towels. Reserve the oil.
Increase the heat of the grill to high.
Remove the shrimp from the marinade, season with salt and pepper and grill until golden brown on each side, about 1 1/2 minutes per side. Remove the shrimp from the skewers, transfer to a platter and drizzle with some of the reserved garlic oil and the garlic chips. Sprinkle with the remaining thyme and garnish with oregano leaves.