In a large bowl, beat the butter, sugar, and vanilla extract until creamy and smooth.
Add the egg and mix until fully incorporated.
Add the flour, baking powder, and salt to the wet mixture. Mix with a spatula or your hands until a smooth dough forms. Avoid overmixing.
Divide the dough into three portions to color.
Portion 1: Leave uncolored (base dough).
Portion 2: Add a few drops of red food coloring and mix until a soft pink tone is achieved.
Portion 3: Add more red food coloring to achieve a brighter pink, or red color. Wrap each portion in plastic wrap, flattening slightly, and freeze for at least 3 hours or until firm.
When ready to make the cookies, remove the cookie dough from the refrigerator and let it rest for a few minutes so that it's easier to work with.
Roll out the uncolored dough between parchment paper, using a bit of flour to prevent sticking. Roll to about 1/2 inch thick. Set aside.
Repeat with the pink and red doughs, but roll these sections a little thinner as they will be layered on top of the base color.
Create the mosaic design by layering the colored cookie dough on top of the base dough.
Use a small heart-shaped cookie cutter to cut multiple shapes from the pink and red doughs.
Place these small hearts onto the uncolored dough, alternating colors to create a mosaic effect.
Place parchment paper over the assembled dough and gently roll over it with a rolling pin to press the shapes together without distorting them.
Use a large heart-shaped cookie cutter to cut-out the cookies. Transfer them to a baking sheet lined with parchment paper.
Chill before baking. Place the cut cookies in the freezer for 5 minutes to help them hold their shape during baking.
Preheat the oven to 350 °F (180 °C).
Bake the cookies for 7–8 minutes, or until the edges are firm but not browned.
Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
Keyword colorful, mosaic, multi-color, sugar cookie, Valentine's Day