Nan always used to have a jar of this handy in the fridge. I have tried to recreate it from memory, but hope that I have done her justice. You can use it on salads, or as a sandwich spread if making salad sandwiches. It is loaded with sugar though, so limit it if that is a problem for you. You will need a jar with a well fitted lid.
1 tin sweetened condensed milk
1/2 tin of white vinegar
3/4 tsp mustard powder
1 tsp chopped fresh mint
Put the condensed milk into a jar. Pour the vinegar and mustard powder into the tin, mix well and pour into the jar. Put the chopped mint into the jar. Put the lid on the jar, and holding it securely, shake. Store in the fridge.