Heat the oil and shallots in small saucepan over medium heat; cook and stir shallots until translucent, about 3 to 5 minutes.
Stir in coconut milk, ginger, lime juice, lemongrass, lime leaves, fish sauce and sriracha.
Bring to a simmer; cover and cook 10 minutes, stirring occasionally.
Remove from heat; discard lime leaves.
Puree the mixture with an immersion blender (or cool slightly and puree in a blender or mini food processor).
Stir in lime zest and sea salt; set aside.
Note: Glaze can be made up to 2 days ahead and held refrigerated. Warm in microwave oven before serving.
Preheat oven to 350°F .
Add all brittle ingredients, except butter, to a medium bowl; stir to combine.
Using a pastry cutter (or 2 forks), cut butter into mixture until it resembles cornmeal.
Spray-coat a parchment-lined 9”x13” pan.
Add mixture to pan; press mixture to edges.
Bake until deep golden brown, about 20 to 25 minutes, turning pan about half way through cooking time to ensure even browning.
Cool at room temperature, then crumble into small granola-like pieces.
Set aside or store in airtight container, if not using immediately.
NOTE: Brittle can be made up to 2 days ahead and held in airtight container.
Cut off shoulder piece from each crab leg; set aside.
Using sharp kitchen shears, cut the underside of crab shell along one side of the leg, then along the other side of each leg.
Lift and remove that shell to expose the crabmeat.
Repeat for remaining legs.
Heat grill to medium-high heat (400°F).
Place crab legs, shell side down, on grill to heat through, about 3 minutes.
Add crab shoulders.
Brush crabmeat with peanut oil-white pepper blend.
Turn legs over and grill 30 to 60 seconds, just until heated through.
Remove crab from grill.
Cut legs at joint to separate.
Brush half of glaze on exposed crabmeat; reserve remaining glaze for spooning on crab at table.
Stack legs on a serving plate, lincoln-log style, if desired.
Sprinkle legs with brittle and green onions.
Garnish with lime wedges.
Serving Size 4 to 6 Servings