Bring 3 quarts of salted water to a boil in a medium saucepan. Blanche the brussels sprouts halves in the boiling water for 2 minutes, covered. Drain and rinse with cold water.
Over medium heat, melt 1 Tablespoon butter in a medium saute pan and add the bacon and onion. Saute until the bacon is nearly cooked and the onion is translucent, stirring frequently, 5 - 8 minutes.
Push the bacon and onion to the edges of the pan and arrange the brussels sprouts in the pan in a single layer, with the cut side down. Leave them in the pan without stirring, letting them brown slightly, about 5 minutes.
When brussels sprouts have caremelized, add the cider, chicken broth and sugar. Turn heat to med-high and bring the mixture to a medium boil. Cook until the liquid has reduced to a glaze and the brussells sprouts are cooked. If too much liquid boils away before brussels sprouts are tender, add additional liquid.
Taste for salt level and season with salt and pepper. Add more sugar if desired.
Remove from heat and stir in the remaining Tablespoon of butter until it is incorporated into the glaze.