Instead of the rum, you can use 1/2 cup water mixed with 1 teaspoon rum extract.
A liquor distilled from fermented sugar cane juice or molasses, rum varies in color and flavor depending on where it’s produced. Puerto Rico’s white and silver rums are light in body and flavor; Jamaican and Cuban rums tend to be more dark, rich and full-bodied.
Remove the skins from the pearl onions quickly by dunking them in boiling water for about 30 seconds. Once cool enough to touch, the skins will slip right off.