In a large pot, render the bacon until crispy, about 5 minutes. Add the onions and cook for about 6 to 7 minutes or until the onions are wilted. Season the mixture with salt, pepper and pinch of cayenne. Add the shallots and garlic and cook for 2 minutes. Stir in the beer, vinegar, and molasses. Stir in the greens, a third at a time, pressing the greens down as they start to wilt. Cook the greens, uncovered for about 1 hour and 15 minutes.