In a bowl, place flour, 1/4 cup of beer, salt, garlic powder, and pepper flakes, if desired. Whisk until combined and smooth. If the batter is very thick slowly add 1/4 cup beer, until it is a dunk able consistency.

Place teriyaki sauce in a microwave safe bowl and add 1 Tbs water. If your Teriyaki sauce is already thin, there’s no need to add the water. Heat it for 30 seconds, and mix until combined(alternatively, you can heat it in a small pot on the stovetop).

Heat up canola oil in a small pot.

Dip quartered mushrooms into the tempura batter and gently place into the hot oil, leaving space so the mushrooms aren’t touching. Fry for about a minute on each side, until they are just starting to turn golden. Remove with a slotted spoon and place onto a paper towel to drain.

Place mushrooms in a serving bowl. Drizzle over Hot Teriyaki Sauce and garnish with red pepper flakes OR place teriyaki sauce in a small serving dish on the side. Enjoy!