Mix maple syrup and raspberries in a small saucepan. Bring to a boil over medium heat. Turn heat down once it starts boiling. Stir often while mixture boils, for about 2 minutes.
Mix water and cornstarch in a small bowl. Once cornstarch has been dissolved in the water, add mixture to raspberries. With the heat still on low, or medium-low, keep stirring mixture until it thickens, about 5 more minutes.
Remove to a bowl. Stir butter in. Wait about 5 minutes, stir vanilla in.