Pour oil into a large pot or deep fryer. Heat oil to 350°F. Line a sheet pan with paper towels. In a small bowl, whisk together tempura batter mix, sriracha and water until blended. Pat cauliflower dry with paper towels. Fry in small batches of 4 to 5 pieces, dipping 1 piece at a time into batter and carefully sliding into hot oil. Deep-fry 2 to 4 minutes until cooked and light golden brown, turning pieces over once. Remove; drain on prepared paper towel lined sheet pan. Skim off cooked batter pieces from oil between batches. In a medium pot, over medium heat, whisk honey, sriracha, sesame oil and butter until sauce is smooth. Toss freshly fried cauliflower with sauce. Garnish with sesame seeds.