Cook the onions in half the butter for a few minutes until softened but not coloured. Leave to cool. Mix the beetroot with the potatoes, add the onions and season with salt and pepper. Stir well. The mix will be a shocking pink colour. It can now be fried as one large cake (the classic bubble) or shaped into small cakes. Pre heat a frying pan. Dust the bubble cakes with a little flour and fry in the remaining butter over a medium heat for about 4-5 minutes until golden brown on each side. Variations - this can become a black pudding and beetroot cake by dicing and frying some black pudding and bacon (or pieces of sausage) and adding it to the mixture before frying it. Serve with a fried egg on top and grilled tomatoes. To make potato and onion bubble, top it with slices of corned beef and thick slices of tomato, season and dot with butter then pop under the grill. If youre feeling really mad, top the lot with slices of cheddar and let it melt over the bubble.