In a large 4-quart (3.8 liters) Dutch Oven or stock-pot, add the olive oil (or butter and melt) and heat until shimmering.
Add the leeks and cook, stirring frequently on medium-low until they're soft with a bit of golden color, about 10 minutes.
Add the cabbage to the leeks. Cook on medium low stirring occasionally to cook down, about 9-10 minutes.
Add garlic, ½ teaspoon salt, broth, potatoes and thyme bundle.
Bring to a simmer, then cook on a low simmer for about 20 minutes for a fork tender potato, or 40 minutes to let the potatoes soften further.
Remove the thyme bundle, stir in the beans and a good squeeze of lemon.
Warm through, about five minutes. Taste to adjust salt and pepper seasoning as needed.
Garnish with shaved parmesan and fresh thyme leaves if desired.
Store in a lidded container in the refrigerator for up to three days. This soup is freezer friendly.
