- Combine ingredients for shrimp in a bowl and stir to coat. Refrigerate and marinate for 30 minutes.
- While shrimp marinates, heat olive oil in a medium skillet over medium heat for 2 minutes. Add plantains to hot oil and cook for 2 minutes on each side. Transfer plantains to a plate to cool slightly. Leave oil in pan.
- Place 2 pieces of plantain between a sheet of parchment paper and press to flatten with the bottom of a mug.
- Return pan to stove and heat over medium heat. Add plantain slices to pan and cook for 3 minutes on each side, until lightly browned and crisp. Transfer to a large plate and sprinkle with salt.
- Mash avocado in a bowl until just slightly chunky. Stir in remaining ingredients for guacamole. Set aside.
- Preheat grill to 400°F. Drain marinade and place shrimp in a grilling basket or tray. Place directly on grill and cook 10-12 minutes until shrimp is cooked through, stirring halfway through cooking. Cool shrimp for 5 minutes.
- Spread a spoonful of guacamole on each plantain toston and top with a piece of shrimp. Serve right away.