Place a heavy-bottomed saucepan over medium heat, add oil followed by the garlic, gently cook for 1 minute. Add butter and melt. Stir in onion, leek, celery and carrot, gently cook for 10-15 minutes. Add potato and cook for 5 minutes more, stirring gently.
Add stock, bay leaf and thyme, securing end of twine around the saucepan handle. Gently simmer for 40 minutes until vegetables break easily. Lightly pulse the soup with a hand blender, half blending the soup.
Place soup back on heat and add cooked pearl barley, bacon and cabbage to the pot. Simmer for 10-15 minutes until cabbage is tender.
Stir in parsley and season to taste. Serve with crusty sourdough bread or homemade brown bread.