Carrot Mango Broth: Place all ingredients in a medium saucepan and boil over high heat until reduced by 1/2. Strain and season with salt and pepper to taste.
Crab cake: In a skillet over low to medium heat, heat 2 tablespoons olive oil and saute the onion and jalapenos until translucent. Remove from the heat and set aside. In a mixing bowl, combine the crab, onion mixture, horseradish, mustard, creme fraiche, egg and salt and pepper, to taste. Refrigerate, covered for 1 hour or up to 1 day. Form the chilled crab mixture into 12 (2-inch) patties 1/2-inch thick and dredge in the corn chips. Heat the remaining 4 tablespoons olive oil in a large skillet over medium heat and fry the cakes for about 3 minutes on each side, or until crusty and lightly browned. Ladle some of the carrot-mango broth into medium shallow bowls. Place 2 crab cakes in the bowl and garnish with green onion and serve with mango relish.
Mango-Green Onion Relish:
Combine all ingredients in a medium bowl and season with salt and pepper.