Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.

Cream together the softened butter and brown sugar until light and fluffy using an electric mixer.

Beat in the molasses and egg until well combined.

In a separate bowl, whisk together the flour, baking soda, ginger, cinnamon, cloves, allspice, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Stir in the crystallized ginger (if using).

Cover the dough and refrigerate for at least 30 minutes (or up to 2 days).

On a lightly floured surface, roll out the dough to about ¼ inch thickness. Use cookie cutters to cut out desired shapes. Reroll scraps.

Place cookies onto prepared baking sheets, leaving about 1 inch between each cookie. Bake for 8-10 minutes, or until edges are firm and lightly golden brown.

Let cookies cool on baking sheets for a few minutes before transferring them to a wire rack to cool completely.