Tempura mushrooms

For the mushrooms

300 g oyster mushrooms 1 liter sunflower oil for frying

For the tempura batter

150 g corn flour 250 g all-purpose flour 660 ml cold beer (2 cans)

For the homemade mayo

2 egg yolks (room temperature) 1 tsp mild mustard 200 ml sunflower oil (or neutral oil) 2 tbsp lemon juice Salt Pepper

To serve

Lemon zest