1. Combine first 3 ingredients in a food processor; process until finely ground. Stir in ketchup, sugar, bean paste, and juice. Place crabs in a large bowl; top with 1/2 cup chile mixture. Toss to combine. Set remaining chile mixture aside. Marinate in refrigerator 1 hour.
2. Preheat grill to medium-high heat.
3. Remove crabs from marinade; discard marinade. Arrange crabs, shell sides up, on grill rack; grill 12 minutes or until shells turn red. Serve with remaining chile sauce and onions. Garnish with cilantro, if desired.
Wine note: Always a good bet with seafood, gewürztraminer pairs perfectly with Chile Crabs. The lychee and spice flavors of Chateau Ste. Michelle Gewürztraminer Columbia Valley 2008 ($10), from Washington, complement the Asian flavors, while the wine's slight sweet apple and pear fruit counter the heat. --Jeffery Lindenmuth