Start by preheating your oven to 350°F (175°C). In a mixing bowl, cream the softened butter with both sugars until fluffy. Then, mix in the egg and molasses until well combined.
In another bowl, whisk together the flour, baking powder, and all the spices. Gradually add the dry ingredients to the wet mixture, blending until you have a smooth dough.
Roll the dough into small balls, about the size of a walnut, and place them on a baking sheet lined with parchment paper, spacing them a couple of inches apart.
Bake for about 15 minutes, until the edges are just starting to crack. After baking, let them cool slightly before dusting with powdered sugar.
Notes
These cookies are especially delicious when allowed to rest for a day, as the flavors will deepen and meld beautifully.