In a medium bowl, whisk together the mayonnaise, buttermilk, parsley, green onion, mint, and garlic. Stir in hot sauce, rice wine vinegar, and salt and pepper to taste. Adjust seasoning as needed. Place in the refrigerator.

In a wide, shallow bowl, whisk together the flour, cornstarch, scant teaspoon of salt, chili powder, and some black pepper. While stirring, slowly pour in the beer, a bit at a time, until you have a batter the consistency of pancake batter (you probably won’t use all of the beer). 

Line a large baking sheet with paper towels. Pour 3 inches of canola oil into a heavy pot or Dutch oven and attach a thermometer to the side of the pot. Heat over medium heat until the thermometer reads 365℉.

When the temperature is reached, dip the onion rings into the batter and swirl around in the bowl to coat. Immediately transfer the onion ring into the hot oil, taking care not to crowd them to avoid sticking. Fry about 3 minutes, until golden brown. Use a slotted spoon to transfer the onion rings to the paper towel-lined baking sheet. Let the oil go back up to temperature before starting to fry the next batch. 

Sprinkle the onion rings with salt, and serve with the buttermilk ranch dressing and lemon wedges.