Butter six 1/2-cup baba molds or muffin tins. In the bowl of a standing mixer fitted with a whisk, combine the eggs, sugar, salt and the remaining flour. Add the softened butter and beat on medium speed for 10 minutes. Add the yeast mixture and the water and beat for 1 minute. Using a rubber spatula, scrape the dough from the whisk and scrape down the side of the bowl. With moistened hands, fill the prepared baba molds two-thirds full with the yeast dough. Set the molds in a warm place and let rise until the dough just reaches the rims, about 20 minutes.