Bring a pot of lightly salted water to a boil. Cook haricot verts about 5 minutes; drain and set aside.
Cook bacon, cut crosswise into 1/4-inch slices, in a large nonstick skillet over medium-high heat for 8 minutes or until crisp. Remove to a paper towel-lined plate with a slotted spoon.
Melt unsalted butter in skillet. Add Brussels sprouts, trimmed and cut from top to bottom into 1/4-inch slices, to skillet and sprinkle with salt and pepper. Cook, stirring, for 5 minutes or until lightly browned. Stir in haricot verts and bacon, and cook until warmed through, about 2 minutes. Sprinkle with additional salt, if desired.