Make mayonnaise: combine all mayonnaise ingredients in a small bowl; stir well to blend; cover and refrigerate until ready to use.
Prepare a med-hot fire in a charcoal grill with a cover; or preheat a gas grill to med-high.
Make the patties: place the almonds in a small fire-proof skillet on the grill; stir frequently until lightly golden brown, 5-10 minutes; set aside to cool.
In a bowl, combine the chicken, egg whites, green onion, and apple; season with salt and pepper; mix well.
Divide mixture into 6 equal portions; shape each portion into patties to fit the rolls.
Finely chop the toasted almonds and combine with the bread crumbs and curry powder in a shallow bowl/pie plate, stirring well.
Coat both sides of the patties with the almond mixture, pressing gently to adhere.
Brush the grill rack with vegetable oil; place the patties on the grill rack, cover, and cook, turning once, just until the juices run clear when the patties are pierced in the center (about 4 minutes on each side).
During the last few minutes of cooking, place the rolls, cut side down, on the outer edges of the rack to toast lightly.
Assemble burgers: decoratively fan several spinach leaves on the bottom roll; top each with a patty and a generous dollop of the mayonnaise; add the roll tops and serve.