I've made both of these from Nigel Slater, blatant copy and paste below from the guardian. Tomato one was ace with fishcakes, the mushroom one was great with burgers.
TOMATO KETCHUP
This is not really a "keeping ketchup", and is something to store in the fridge. Makes about 750ml.
red onions 2
groundnut oil a little
fresh red chilli medium sized
tomatoes 800g
caster sugar 3 tbsp
malt vinegar 2 tbsp
star anise 2
Szechuan peppercorns 1 tsp
ground paprika 1 tsp
black mustard seeds 1 tbsp
Dijon mustard 1 tbsp
Peel and thinly slice the onions. In a heavy pan, over low heat, warm a thin film of oil, add the onions and sweat, stirring occasionally, for five minutes. Roughly chop the red chilli and 600g of the tomatoes, then blitz the remainder in a food processor or blender, to a thick scarlet slush.
Add the sugar to the pan and continue to cook until the onions are dark and sweet, then add the vinegar and both chopped and blitzed tomatoes. Bring to the boil, add the star anise, lower the heat and continue cooking at a moderate simmer. Finely grind the Szechuan peppercorns, stir them in, followed by the ground paprika, mustard seeds and Dijon mustard. Add a good grinding of salt, then continue to simmer for 15 minutes, until the tomatoes will collapse when pressed against the side of the pan with a spoon.
Remove the ketchup from the heat, spoon into clean jars, seal, cool and refrigerate.
MUSHROOM KETCHUP
A thick, slightly rough textured ketchup to accompany grilled steak or lamb. Makes 300-400ml.
small mushrooms 250g
garlic 3 cloves, peeled
cider vinegar 3 tbsp
caster sugar 3 tbsp
spring onions 5, finely chopped
anchovy fillets 15
large gherkins 3
Dijon mustard 2 tbsp
In a food processor combine the mushrooms, garlic and cider vinegar to a coarse purée then scrape into a heavy saucepan over a moderate heat. Stir in the sugar and spring onions and simmer, stirring regularly till the onions have softened. Ignore the slightly unappetising look - it is early days.
Roughly chop the anchovy fillets and gherkins, add to the pan with a generous grinding of black pepper, and continue to cook for 10 minutes, stirring regularly. Add the mustard, stir and leave to simmer for a further 5 minutes. Adjust the seasoning, it should be sweet, sharp and salty, then serve with grilled steaks or lamb.