Roughly chop the starter to cut the onions into smaller pieces. Combine the starter, broth, water, and butter in a medium saucepan over medium heat. Warm, stirring frequently, unil the butter is melted and the onions seperate from each other, about 5 minutes. Because some broths are saltier than others, taste the onion nand broth mixture; it should be noticeably but pleasantly salty. Add more salt if necessary (remember, the onion and broth mixture will season the rice, too; I typically add 1 teaspoon of salt.)