Preheat oven to 400°. Pulse cauliflower florets in a food processor until finely chopped. Spread on a baking sheet; bake at 400° for 40 minutes, stirring occasionally. Combine cauliflower, prepared risotto reserved from Sweet Onion Risotto with Sautéed Kale, panko, parsley, salt, pepper, fontina cheese, and egg; shape into 8 (3-inch) patties. Heat 1 tablespoon olive oil in a large nonstick skillet over medium heat. Add 4 patties to pan; cook 3 minutes on each side. Remove from pan. Repeat procedure with 1 tablespoon olive oil and remaining 4 patties. Combine mayonnaise, lemon juice, chives, and minced garlic. Serve with patties.