2 tablespoons vegetable oil
1 onion, grated
1 cup mild American yellow mustard
2 cloves garlic, crushed
1 teaspoon Worcestershire sauce
1½ teaspoons dry English mustard
1 tablespoon tomato paste
2 tablespoons brown sugar
¼ teaspoon cayenne pepper
⅓ cup cider vinegar
½ cup water
sea salt and freshly ground pepper
Heat the oil in a medium saucepan and add the onion and a pinch of salt. Cover and cook for 10 minutes until the onion is very soft.
Combine all the remaining ingredients in a bowl then add to the onion. Season and cook partially covered with the lid for 10 minutes, stirring often to prevent it catching on the base of the pan. Cool.
For a smooth sauce, place in a food processor and process until smooth or leave as is for a rougher textured sauce. Makes about 2 cups