Gather all the ingredients.
In a food processor, blend ponzu, boiled Japanese sake, onion, sweetener, garlic cloves, and neutral-flavored oil until smooth to make the sauce.
Add diced onions and butter to a skillet and cook for 2 to 3 minutes until browned. Remove from the pan and set aside.
In a mixing bowl, combine the ground pork, ground beef, grated garlic, panko, salt, black pepper, egg, half & half, nutmeg, and the browned onions. Mix well with your hands until evenly combined.
Take half of the mixture and gently toss it between your hands to shape it into a ball, then press it into a 1-inch thick patty. Use your thumb to make a small indent in the center to help it cook evenly. Repeat with the remaining mixture and set aside.
Lightly coat a large skillet with cooking spray and heat over medium heat. Add the patties with the indent side up, cover, and cook for 3 to 4 minutes until browned. Flip and cook the other side until browned and cooked through.
To serve, place a hamburger patty over a bowl of rice, drizzle with the wafu sauce, and garnish with chopped green onions and grated daikon.