Sift the flour and baking powder together and set aside.

Beat the butter and sugar to soft (not light and fluffy). Add the heavy cream and continue to mix. Slowly, spoon in the flour mixture and mix just until the ingredients combine. Wrap the dough in a plastic wrap and refrigerate for at least 30 minutes.

Preheat the oven to 175°C/350°F. Line a baking tray with parchment (baking) paper.

Remove the dough from the refrigerator and let stand at room temperature for 10 minutes. On a lightly floured work surface, tip the dough and fold it a few times to make it pliable. Using a rolling pin, roll out the dough into a sheet, about 1/4-inch thick, and cut into desired shapes. Lift the dough cutouts with a flat spatula and arrange the cookies on the prepared baking tray, spacing them 1-inch apart.

Bake the cookies until the edges just begin to brown, about 8-10 minutes (remember to turn the tray back side front halfway through baking). Remove the cookies from the tray and let cool completely on a wire rack.

Prepare small cones with parchment paper to pipe the icing. To prepare the royal icing, whisk the egg white and lemon juice at medium speed until foamy. Slowly spoon in the sugar and beat until thick and glossy. Divide the icing into as many colors as desired and add the color drop-by-drop, until the desired color is attained. Cover the icing immediately, as it dries out really fast. To change the consistency of the icing, thin it with a few drops of warm water or thicken it with some more sugar. Fill some icing in the prepared cones to pipe out patterns.

Using a flat spatula or a butter knife, coat the cookies with the base color icing. To merge the second shade into the base, drop or pipe another color while the base coat is still wet. Run a toothpick through the colors to create swirls. To create an embossed look, pipe the second shade after the base coat is dry.

Let the cookies dry completely, about 2 hours and store in airtight containers for up to two weeks.