Heat butter in saucepan and fry the bacon. Add diced carrot, onion, leek, garlic, bay leaf and thyme. Cook to soften vegetables, without browning. Add the drained and rinsed peas to the saucepan, then the stock. Add salt and pepper (having tasted first).
Simmer until the peas are soft and mushy. This will usually take up to 2 hours. Remove soup from heat and reduce to a fine puree using a blender or liquidiser. Finish by adding a little cream to taste.
Reboil the soup and serve piping hot with croutons sprinkled on top.