Sweat the diced onions with the red and green peppers in a small amount of olive oil.
When the onions are soft, stir in the garlic, chillies and season with paprika, cayenne chilli pepper, salt and pepper.
Add 2-3 tbsp of water to the saucepan, cover with a lid and simmer for 10 minutes.
Keep aside to cool.
Cook the yellow onions
Peel and cut the onions lengthwise and in half.
Place the cut side of the onion down in the skillet over a high heat with a drizzle of olive oil and a pinch of salt for 10-12 minutes until caramelised.
Flip the halved onion over and cook for another 10-15 minutes or until soft.
Prepare the patty
Choose a pastry ring (or round cutter) the same size as the bread bun.Press down the vegan mince to shape it into a burger patty.
Pan fry or grill the vegan mince patty with some oil, flip the patty over and cook through.
Assemble the burger
Toast the bun in the oven. Spread some vegan mayonnaise on the toasted patty.
Arrange the fresh spinach leaves and a large spoon of cooked peppers relish on to the bottom bread.
Place the cooked patty on top with the caramelised onions, avocado slices and mixed coleslaw.
Notes
Caramelise the halved onion in the oven at 200°C, it is easier than pan-frying.
Add a pinch of sugar to accelerate the caramelising process.