In a bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar at medium speed until light and fluffy. About 2 minutes. Add the egg and molasses, mix until well incorporated.
In a separate bowl, whisk together the flour, baking soda, salt, ginger, cinnamon, nutmeg, and cloves. Add to the butter mixture, with the mixer at low speed, mixing until combined and a dough is formed.
Wrap the dough with plastic film and refrigerate for at least 1 hour.
Preheat oven to 375°F and line baking sheets with parchment paper.
Take the dough out of the refrigerator, and flour a clean work surface. Roll the dough to ¼-inch thick. Using a gingerbread cookie tree cutter set, cut out two of each size of stars. Place the cut-out cookies on prepared baking sheets. Keep similar sizes of stars on the same baking sheets, so they bake evenly. Space the cookies about 2-inches apart. Bake the smaller cookies for 10 minutes and the larger cookies for 12-14 minutes, until light brown.
Remove from oven. Allow resting on baking sheets for 5 minutes. Transfer the cookies to a wire rack to cool completely.
Prepare the royal icing. Combine all ingredients together in the mixing bowl of an electric mixer. Beat on low speed using the whip attachment until combined. Increase speed to medium high and beat for 5 – 8 minutes, adding 2-3 tablespoons more warm water, as necessary. Icing should have a medium consistency. Should flow but not runny. Ice cookies and decorate with edible pearls and sanding sugar. Allow the icing to set for about 1 hour. Add powdered sugar to leftover icing until it achieves a thick consistency.
Assemble centerpiece. Place the largest star on a serving platter. Pipe thick icing on the center of the cookie, top it with the other cookie that matches the size, but pointing in a different direction. Repeat the process with the remaining cookies. When you get to the top, set one of the smallest stars up. Allow the centerpiece to dry for about 1 hour before moving.