Pre-heat oven to 350 degrees and line a 9-inch cake pan with parchment paper.
In the bowl of a stand mixer or in a large bowl with a hand mixer, cream together butter and sugar until well combined.
Beat molasses and egg into mixture.
In a separate large bowl, whisk together flour, baking powder, ginger, cinnamon, ground cloves, and salt.
Add the dry mixture to the wet ingredients and mix until just combined.
If using white chocolate chips, fold into the batter.
Press cookie dough into the prepared pan, as evenly as possible.
Bake at 350 degrees for 20-24 minutes, until edges are turning golden, but cookie cake is still soft in the middle. Remove from oven and place pan on a wire rack to cool. Once cooled, use a knife to loosen edges of cookie and turn out onto a plate or cake platter.
Put frosting in a pastry bag and pipe along the edges. Sprinkle on crushed peppermint candies or other holiday decoration.