In a mixing bowl combine the crabmeat, mayonnaise, mashed avocado, lime juice, salt, and white pepper and fold gently to combine, trying to retain as many lumps of crabmeat as possible.
Place the flour in a small bowl and season lightly with salt and white pepper. In a second bowl combine the eggs and milk; whisk to combine and season lightly with salt and white pepper. In a third bowl place the panko bread crumbs.
Using a measuring cup as a guide, divide the crabmeat mixture into 8 equal sized portions, about 1/3 cup each, and, using your hands, form into cakes about 3 inches wide and 1-inch thick. Working 1 at a time, dredge the crab cakes into the flour, then into the egg wash, and finally the panko crumbs, shaking between each stage to remove excess. Place breaded cakes onto a parchment-lined baking sheet and refrigerate while you prepare the mango-papaya salad, at least 15 minutes.
Chef's Note: These crab cakes are fragile and will require caution when breading. After breading and refrigerating they will be easier to handle.
In a large mixing bowl, combine the mango, papaya, poblano, and napa cabbage. In a blender combine the cilantro, jalapeno, garlic, lime juice, fish sauce, and brown sugar and blend until smooth. Toss the mango-papaya mixture with the dressing and season, to taste, with salt and white pepper. Set aside, refrigerated, while you cook the crab cakes.
Heat a large skillet with 1/2-inch of vegetable oil over medium to medium-high heat. Add the crab cakes, in batches if necessary, and cook until golden brown and crispy on both sides and heated through, about 2 minutes per side. Transfer to paper towels to drain briefly before serving. Repeat with remaining crab cakes, if necessary.
When ready to serve, place some of the mango-papaya salad in the center of 4 plates and lean 2 crab cakes against the salad. Garnish with the toasted macadamia nuts and serve immediately.