Season the shrimp with the combined spices. Set a heavy 10-inch skillet over medium-high heat for 1 minute. Add the oil and shrimp and sauté, stirring occasionally, until the shrimp are opaque and firm to the touch, about 2 minutes. Transfer to a cutting board and cut in half lengthwise.
Pit the avocados and scoop the flesh into a small bowl. Add 1 Tbs. lime juice, the chopped cilantro. Mash with a fork until relatively smooth and season with a heaping 1/2 tsp. salt and a few grinds of pepper.
Spread the mashed avocado over the toasts and slice each toast into four even rectangles. Top each with two halved pieces of shrimp and serve.
