Put oven rack in middle position and preheat oven to 200°F. Line a baking sheet with paper towel
Pulse avocado with mayonnaise, lime juice, salt, sugar, and one fourth of chile in a food processor until chile is finely chopped. Add milk and purée until smooth. Add more chile if desired, processing until smooth. Transfer sauce to a bowl and chill, covered.
Stir together crabmeat, mayonnaise, chives, lemon juice, mustard, pepper, and 1 tablespoon panko in a large bowl until blended well, then chill, covered.
Melt butter in a medium nonstick skillet over moderate heat, then cook garlic, stirring, until golden and fragrant, about 2 minutes. Add herbes de Provence, salt, and remaining 7 tablespoons panko and cook, stirring, until golden brown, about 6 minutes. Transfer crumbs to a plate to cool. Discard garlic.
Divide crabmeat mixture into 4 mounds on a sheet of wax paper. Form 1 mound into a patty, then carefully turn patty in crumb mixture to coat top and bottom.
Transfer to a baking sheet and repeat with remaining 3 mounds, then sprinkle remaining crumbs on top of crab cakes.
Put ¼ cup oil with 2 tbls butter in skillet. Shoulder fry the crabcakes until brown on the sides. Serve with sauce and a veg/salad.
