In blender, combine strawberries with 1/4 cup syrup and process until smooth. Transfer to large bowl, and stir in yogurt until well combined.
Divide mixture among fluted tart molds. Insert wooden pop stick into each mold. Freeze 3 hours, or until frozen through. Just before serving, roll umbrellas in sprinkles, if using.
In small saucepan, combine and simmer water and sugar until sugar is dissolved, about 4 minutes. Set saucepan in bowl of ice water until syrup is cool.