Separate the mushrooms into smaller bunches if needed. Pat them dry with a paper towel.
In a large mixing bowl, whisk together Mushroom Coating ingredients as listed. Add a few mushrooms into the mixture and dust them until evenly coated. Set aside.
In another large bowl, combine Mushroom Batter ingredients. Mix and set aside.
Heat 2-inches of oil in a large pan on medium-high heat. Place a wooden chopstick into the hot and if bubbles form, it's time to fry.
Dip mushroom into the batter and carefully lower it into the hot oil away from you. Fry in small batches on both sides until golden brown and crispy, about 3-5 minutes. Do not overcrowd the oil.
Remove fried mushrooms with a slotted spoon. Transfer to a wire rack or paper towel lined plate allowing excess oil to drip off. Then transfer to a large serving plate.
In a small bowl, combine Sweet and Sour Sauce ingredients as listed. Set aside.
In a large pan or wok, heat 1 tablespoon of vegetable oil on medium-high heat. Fry onions, bell peppers and pineapples until softened.
Pour sauce into the pan and let it come to a boil and simmer until sauce has thickened. Mix and pour your sauce over the battered mushrooms. Serve & enjoy!