Mix the flour and baking powder in a mixing bowl, add the eggs, milk and beer and beat everything vigorously with the whisk.
Divide the broccoli into small florets, cut the stems crosswise and briefly blanch the vegetables in boiling salted water until they are firm to the bite, remove and dry on paper towels.
Peel the onion and cut into approx. 0.5 cm thick rings, only use the outer (large) rings.
Heat a small saucepan with the rapeseed oil (or other deep-frying fat) to approx. 140 ° C. Turn the vegetables in the batter and add them to the saucepan. It has to swim in the boiling fat. When the vegetables have turned golden, remove them with a slotted spoon.