Ingredients

Equipment
Sharp Knife & Chopping Board
Medium Sized Mixing Bowl
Large Shallow Dish
Pot (suitable for deep frying)
Slotted Spoon & Tongs
Tray & Paper Towels
Kitchen Thermometer
Ingredients
1 large White Onion, peeled & very thinly sliced (see notes)
2 cups / 500ml Buttermilk, or as needed to cover onions (see notes)
1 1/2 cups / 225g Plain / All Purpose Flour
1 1/2 tsp EACH: Paprika, Baking Powder
3/4 tsp Salt (plus more to serve)
1/4 tsp White Pepper
4 cups / 1 litre Vegetable Oil, or as needed

Instructions

In a medium sized mixing bowl combine onion slices and enough buttermilk to comfortably cover them. Leave to soak for 30-60mins. If you're short on time just leave to soak as you prep the other steps.
In a large shallow dish combine flour, paprika, baking powder, salt and white pepper. Use tongs to grab a small batch of the onions, give them a good shake to remove excess buttermilk, then add into the flour. Use a fork or your hands to fully coat them as best you can. Give them a shake to remove excess flour, place on a tray then repeat.
Heat up oil in a suitably sized pot or pan to 180C/350F. Carefully lower in a batch of the onions and use tongs to immediately separate them if they stick together. Fry until deep golden and visibly crispy (around 2-5mins depending on how thick the slices are and how many you fry at once). Use a slotted spoon to remove them and place on paper towels then repeat. Bring temp back up to 180C/350F between batches. I find 3 batches works fine, just don't overfill the pot or the oil temp will drop too much and they'll all stick together.
Sprinkle over salt to draw out the final bit of moisture then serve up in sandwiches or as finger food with a dip!
Notes
a) Buttermilk - You'll find this in most stores in the milk/cream section. If you can't find it you can make your own by combining 1 cup milk with 1 tbsp acidity (lemon juice, white vinegar). Leave it 10mins to slightly curdle then use as needed.
b) Onion slices - I usually slice them into very thin rings, almost like mini onion rings. You can do regular slices though. The main thing is that you properly separate all the onion strands before adding into the buttermilk or they'll clump up as you dredge/fry them. To get the slices nice and thin you can use a mandoline or a nice sharp knife.
c) Storage - I find these are best served fresh, but for the best chance of them lasting I recommend storing them in an air-tight container or zip lock bag for up to a week (or until they start to soften).
d) Serving - Great in a sandwich (like my Grilled Chicken Sandwich), perfect with a dip (like Chipotle Mayo), but also great on burgers, salads and casseroles.

Sandwiches