If making up to 2 days ahead, cover and chill bean mixture and bacon separately. Reheat in a microwave oven or stir often over medium heat.
In a 5- to 6-quart pan over medium-high heat, stir bacon until crisp, about 10 minutes. Lift out with a slotted spoon and drain on towels.
Add beans to drippings in pan; mash with a potato masher or beat with a mixer until creamy. Stir often over medium heat until hot, about 6 minutes.
Meanwhile, coarsely chop spinach. When beans are hot, add spinach; cover and stir occasionally, until wilted, about 3 minutes. Stir in half the cheese. Add salt and pepper to taste. If beans are not as creamy as you like, stir in a little broth. Pour into a bowl and sprinkle with remaining cheese and bacon.