Place the peas in a bowl. Cover with cold water and let soak for at least 4 hours. Ensuring they are always completely covered with water. Slice the leeks and place in a large bowl of water to rid them of any sand or dirt. Scoop the leeks out with your hand or slotted spoon.
In a large pot over medium heat, heat the oil and add the carrots, leek, onion and potato until soft. About 5 minutes. Add the ham, peas, broth, water and thyme. Bring to a boil.
Cover and simmer for 1 hour and 45 minutes. Stirring occasionally. Season with salt and pepper.
For the dumplings
In a bowl combine the flour, baking soda and salt.
Cut in the butter, add the cheese and milk.
Divide the dough in 6 pieces and drop into the boiling soup. Cover and cook for 10-12 minutes.
Recipe by Friday is Cake Night at https://www.fridaycakenight.com/2015/02/pea-soup-with-sharp-cheddar-dumplings/