Render the bacon in a large skillet over medium-high heat, until it begins to get crispy. Add the onions and saute until golden brown. Add the mushrooms and garlic halfway through cooking the onions and brown as well.
Add the herbs and wine and deglaze the pan. Let the liquid reduce by half. Remove the rosemary.
Add the clams and stir. Add the clam juice and chicken stock. Simmer on low for 30 minutes, covered.
Add the potatoes and cook for about 30 minutes more, or until fork tender.
Finish with cream, a pinch of cayenne, a few turns of pepper and salt to taste. Bring to a simmer, turn off the heat and let sit. Letting it sit overnight will improve the flavor even more.