For the stuffed mushrooms: Mix the imitation crab meat, cream cheese, sriracha sauce and three quarters of the diced green onions in a large bowl. Make sure the mixture is well combined to avoid pockets of cream cheese or sriracha sauce. Stuff the mushroom caps with the crab mixture making sure the mixture is packed together tightly. Do not be afraid to overstuff the mushrooms.
Fill a medium saucepan or wok 3 inches deep with oil and heat to 325 degrees F. Divide the tempura batter mix between 2 bowls. In one bowl, add cold water according to the manufacturer's instructions; the mixture should coat the back of a wooden spoon.
In batches, dredge the stuffed mushrooms in the dry tempura batter mix, and then coat in the wet tempura batter. Shake off any excess batter and then carefully place the mushrooms into the hot oil, taking care not to burn yourself or splatter any oil. Fry until crisp, 5 to 8 minutes, and transfer to a plate layered with paper towels. Cooking time can vary wildly depending on the size of the mushrooms, the thickness of the batter and the number of mushrooms placed into the pan at the same time. If in doubt, take out a sacrificial stuffed mushroom and cut it in half. If the center of the crab mixture is still cold to the touch, then the rest of the mushrooms should cook for a while longer. A warm center indicates that the mushrooms are ready.
For the mushroom sauce: Whisk together the soy sauce, oyster sauce and onion powder in a bowl. Add the corn syrup and mix until thoroughly combined.
For serving: Cut the cooked stuffed mushrooms in half, drizzle some of the mushroom sauce on top and sprinkle with the black and white sesame seeds and remaining diced green onions. Serve with the remaining mushroom sauce on the side for dipping.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.