In the bowl of a stand mixer (or in a large bowl, using a hand mixer), cream the butter and cream cheese with the sugar. Beat for several minutes, until light and fluffy. Beat in the egg and vanilla.

Mix the flour, baking powder, and salt in a separate bowl then gradually add to the butter and sugar mixture until fully incorporated and a soft dough is formed.

The dough should now be chilled or frozen. Divide the dough into 2 balls and flatten into disks. Wrap the dough in plastic wrap until ready to use. Refrigerate for at least 1 hour or a few days.

You can also freeze the dough disks. To do this, wrap them in plastic wrap and a freezer bag, for up to 1 month. To thaw, leave in the refrigerator overnight, then proceed with the recipe.

To bake the cookies, preheat the oven to 350°F and prepare baking sheets by lining them with parchment or silicone liners. I also find they bake well directly on the baking sheet.

Remove the dough from the refrigerator 20-30 minutes before you plan on using it so it softens up. Roll the dough on a floured surface to 1/4 inch thick. Cut out heart shapes and place them on the prepared baking sheets.

Bake the cookies for 8 to 12 minutes, depending on thickness. Make sure not to over cook, they will look better if each is a consistent light color. Let cookies cool for 5 minutes on the cookie sheet. Transfer to a wire rack until completely cooled.

Cool completely before icing and adding the sprinkles. Be sure not to stack iced cookies as they may stick to each other.

For the icing: Mix together the powdered sugar, meringue powder and water in a bowl. Add water slowly, this icing will thin out too quickly if not careful. Separate icing into small bowls and color with gel. Use it slightly thicker (like toothpaste) to pipe on the outlines of the cookies. You need these outlines to keep the flood icing on the cookies.) To make the outlines use a very small, round pastry tip (#2 is good) For flooding use a larger tip, an offset spatula or a squeeze bottle. Add a little bit more water to the icing, very small amounts at a time (1/2 teaspoon) until the icing is just thin enough that it runs when you use it. First outline the cookies, then flood them. Carefully add the sprinkles while the cookies are wet, I used my fingers. Let cookies dry completely. To speed things up you can put them in the fridge for 20 minutes.