Heat oven to 425°F. In a small pot, bring 1/2 cup water, butter, sugar, and salt to a boil. Reduce heat to medium. Add flour and stir quickly until a ball of dough forms, about 1 minute. Remove to a bowl. Cool 5 minutes. Stir in eggs one at a time, until dough is smooth.
Transfer dough to a piping bag or resealable plastic bag with the corner snipped. Pipe twelve 1 1/2-inch mounds, spaced 2 inches apart, onto a parchment-lined baking sheet. Smooth out tops with a wet finger.
Bake at 425°F for 10 minutes. Reduce heat to 350°F and bake another 10 to 15 minutes, or until golden brown. Cool completely.
Slice each profiterole in half crosswise. Place a small scoop (about 3 Tbs.) ice cream into bottom of each profiterole, then replace tops. Drizzle with chocolate sauce, if desired, and serve.