Preheat oven to 375 degrees. In the bowl of a food processor, add flour, sugar, salt, and baking powder. Process 15 to 20 seconds to combine. Add butter and process until butter pieces are no larger than a pea. Add egg, water, and vanilla. Process just until mixture comes together into a dough, about 10 seconds. Transfer dough to a clean surface and use hands to finish bringing together. If dough still appears dry and crumbly, add water 1 tsp. at a time until dough comes together. Be careful not to add too much liquid or dough will not hold its shape in the oven. Transfer dough to a cookie press fitted with the desired die. Extrude dough directly to a baking sheet, pressing down firmly until dough forms shape and sticks to baking sheet before pulling up. If dough is too soft and is not separating from the press easily it may need to be chilled briefly. Cover and chill formed cookies for 10 min. Add any sprinkles or decorations and bake for 10 min., or until set and slightly golden brown around bottom edges. Let cool on baking sheet for 10 min., or until cookies come off easily.