Bring beans, stock, and thyme sprigs to a gentle simmer in a medium pot over medium-high heat. Reduce heat to medium-low and simmer, uncovered, skimming any foam from surface, until beans are tender, 1-1 1/2 hours, depending on types (After 1 hour, taste a few beans and cook longer if needed).
Discard the thyme stems, season liberally with black pepper, to your liking, remove from heat, and let sit 30 minutes.
At this point if you don't want to add cream, the beans can be seasoned with salt/pepper or other herbs and then added thyme and oil. But for a creamy, pretty dish, read on:
Return to a low simmer and stir in the cream. Season with kosher salt and more pepper, if needed. Serve topped with thyme leaves, sea salt, and drizzled with oil.
For a hearty, meaty dish, add chunks of uncured ham that you sear for added flavor, or cook some thick pepper bacon or black forest bacon and serve with two pieces placed in an X over the top of beans for nice presentation.
Be sure to include some crusty, chewy bread for dipping.
Make ahead information: Beans can be cooked 3 days ahead. let cool; cover and chill.
How to soak your beans: Sort beans and soak overnight in bowl using 3 times as much water as beans. The next morning rinse beans with cold water.
Cook's note: I measured 2 cups of beans before soaking. The beans increase in volume overnight. I used all the beans for the recipe completion.