Apply a medium coat of SYD chicken rub to the shrimp.
Prepare a grill with hot coals.
Skewer about 5 shrimp on 2 skewers (so the shrimp don't curl as they cook).
Grill the shrimp until just cooked. Try to get some char but be careful not to overcook else it will be rubbery.
Let the shrimp cool enough to handle and roughly chop into bite-size pieces.
Reserve 1 tablespoon green onion tops for garnish later. In a bowl, combine the remaining green onions with the mayonnaise and Sriracha sauce. Mix in the chopped grilled shrimp.
Spoon onto endive leaves, sprinkle with the remaining green onions, and serve.