Beat butter, sugar, and molasses in a stand mixer (or very large bowl with a hand mixer) until smooth. Mix in the egg, then add the vinegar, baking soda, salt, and spices. Mix until combined (mixture may look a bit curdled, that's normal.)

Mix in flour, 1 cup at a time, until dough forms. Divide dough into two or three sections.

Lay out a sheet of parchment paper or wax paper on your work surface. Add half the cookie dough and add a second sheet of paper on the top. Use a rolling pin to roll the dough to 0.25-inch thick, in between the pieces of parchment. Periodically, gently lift the parchment off the layer to make sure it's not sticking. Repeat with second half of dough.

Chill the rolled out dough in the refrigerator for at least 1 hour.

Preheat oven to 375°F. Line two cookie sheets with parchment or silicone baking mats. Cut shapes from chilled dough, placing on the prepared pans. Chill another 10 minutes before baking.

Bake for 8-12 minutes, depending on cookie size. Re-roll any scraps of dough and re-chill and repeat.

Cool cookies completely before frosting.

While cookies are cooling, make the frosting. Add meringue powder, powdered sugar, vanilla, and water to the bowl of a stand mixer. Beat until peaks form and it's lost it's glossy sheen, about 7-10 minutes. Add a bit more water as needed for piping consistency.

At this point you can color the frosting if you want, using food coloring. Frost cookies and top with sprinkles. Let set for at least an hour before stacking.