Bring beer to a boil in a 5- to 6-qt. pot that can hold a steamer basket snugly. Meanwhile, cut potatoes into bite-size pieces and put them in a steamer basket. When beer boils, put steamer basket of potatoes in pot, cover, reduce heat to low, and steam until potatoes are tender when they are pierced with a fork, about 15 minutes.
Meanwhile, cook bacon in a frying pan over medium heat until crisp. Drain bacon on paper towels, chop, and set aside. Pour off fat in pan, but don't wipe out or rinse. Return pan to medium heat and add butter and onions. Cook, stirring occasionally, until onions start to brown, about 10 minutes.
Meanwhile, put potatoes in a serving dish, reserving beer in bottom of pot. Add 3/4 cup beer and reserved bacon to onions, scraping up any browned bits from bottom of frying pan.
Pour bacon mixture over potatoes, add pepper, and stir gently to coat. Add salt to taste. Serve hot or warm.
Note: Nutritional analysis is per serving.