Onion rings with cheese in batter

Ingredients:

• 2 medium onions, peeled and cut into 0.8 cm thick rings.
• 1 cup wheat flour
• 1 cup rice flour
• 1 cup finely grated Parmesan cheese, plus extra for sprinkling
• 3 tbsp mustard powder
• 1 tbsp paprika
• 1 teaspoon garlic powder
• 2 cups of sour milk or kefir
• 1 cup dark beer
• 2 tbsp mustard
• Vegetable oil for deep frying

Preparation:

1. Fill a deep fryer or large cast iron pot with vegetable oil to a depth of 5 cm. Heat to 165° - 170°C.
2. Knead the batter: In a large bowl, combine the wheat flour, rice flour, Parmesan, mustard powder, paprika, garlic powder, and 2 tablespoons salt. In another bowl, combine sour milk, beer, and mustard. Pour 1 cup of the resulting mixture into the bowl with the dry ingredients and knead until smooth and the consistency of pancake batter.
3. First, fry 1 onion ring. Dip it in the batter and fry for 2 minutes until golden brown. If the batter isn't cooked through, it's likely too thick. Add a splash of the liquid mixture you reserved before kneading the batter (you may need to thin it out a bit more after it rests).
4. Dip the onion rings into the batter a few at a time and fry for about 2 minutes until golden brown. Remove the rings from the oil with a slotted spoon and transfer to a wire rack. Sprinkle with Parmesan cheese immediately.