Very traditional way is to make this using left-overs and bone from Christmas ham. Unfortunately I didn't have the possibility use those, or meaty ham bone, but smoked ham works alsmost as good as those.
Split pea soup
For 4-6 person
500 g dried peas
3 l water
1 (large) carrot
400 g smoked ham
1-2 tsp marjoram
allspice and salt to taste
Rinse peas with cold water. Put the peas into a pot or ducth oven, and pour the water. Let peas soak in a water 10-12 hours.
Use the soak water when cooking the soup. Bring to boil, and reduce heat very low.
Peel and chop onion and carrot, dice the ham. Add them into soup, as well as spices. Stir the soup well. Let simmer for 4-6 hours.
Serve with mustard and/or finely chopped raw onion.