Roughly chop the shrimp, reserving about one-quarter of it.
Add the remaining shrimp and garlic to a food processor. Process for about 1 minute until a smooth paste forms.
Add the reserved roughly chopped shrimp and pulse for another 10–15 seconds.
Transfer the shrimp mixture to a large bowl. Add the scallions, panko, and beaten egg. Mix until combined.
Form the mixture into 4 evenly sized burger patties.
Refrigerate the patties for 30 minutes to help them firm up and hold their shape.
Grill the pineapple and red onion over direct heat for 2–3 minutes per side.
Add the roasted pineapple and onion to a food processor with the avocado, cilantro, lime juice, habanero, cumin, salt, and olive oil. Process for 45–60 seconds, then refrigerate.
Heat a cast-iron skillet or griddle to 425°F. Add 1–2 tablespoons vegetable oil and allow it to heat.
Cook the shrimp burgers for 4–5 minutes per side, until crisp and cooked through. The author recommends an internal temperature of 145°F for the shrimp patties.
Toast the burger buns.
Spread Sriracha mayo on the bottom bun, then add a shrimp burger and pineapple habanero salsa.
Add the top bun and serve.