Using a stand mixer fitted with the paddle attachment or hand-held mixer, cream the butter and brown sugar until fluffy and lighter in color. Add the molasses and yolks and beat until smooth.
While things are creaming away, mix all your dry ingredients together. Add your dry ingredients to the creamed mixture and mix until just combined, adding a touch of water if needed to come together.
Roll the dough between two sheets of parchment paper to desired thickness (thinner for crisper cookies, thicker for softer ones) and place on a cookie sheet and into the freezer until firm and cold.
Heat oven to 350F and line two baking sheets with parchment paper. Remove the top parchment paper from your dough and punch out your cookies. Place them ½” apart on your cookie sheets. Bake for 10-12 minutes, or until just setting on the outside edges. Cool completely before removing them from the pans.
ROYAL ICING
Beat all ingredients until smooth. Divide into bowls to color and add a touch of water, if needed, to thin out.