Fry the peppers in a large pan in a little olive oil to soften, then add the mushrooms and garlic and fry for just a few minutes to keep the colour of the peppers bright.
Remove from the heat and add the pine nuts, breadcrumbs and tomato puree, season to taste with salt and a good amount of black pepper, add the Parmesan, beaten egg and chopped parsley. Mix until well combined - the mixture should be sticky and not too dry.
Place the mixture in a loaf tin lined with baking parchment and bake for 45 minutes in a medium oven, until the top is nicely browned. Turn out of the loaf tin and remove the parchment - if you like, you can return it to the oven 'right way up' for 10 minutes or so, so that the top and sides brown.
Serve with warm redcurrant jelly, melted with a little port if you like. Can be made in advance and frozen, or kept in the fridge and warmed through before serving. It's also great sliced and served cold on Boxing Day with more redcurrant jelly or cranberry sauce.