Preheat oven to 350 F / 175 C and line 2 large cookie sheets with parchment paper or silicone mats. Set aside.
Cream the butter, granulated sugar, and light brown sugar in a large bowl with an electric hand mixer or stand mixer fit with a paddle attachment. Mix on a medium-high speed with an electric mixer until the mixture becomes lighter in color (about 2 minutes).
Mix in the egg and molasses on a medium speed until combined. Scrape the sides and bottom of the bowl as needed with a rubber spatula.
Sift the dry ingredients (flour, ginger, cinnamon, baking soda, and salt) into the wet ingredients. Mix on low until just combined. Scrape the sides and bottom of the bowl as needed with a rubber spatula.
Use a cookie scoop or large spoon to scoop and roll 14 cookie dough balls. Use about 3 Tbsp of dough per cookie.
Place the cookies on the prepared baking sheets and bake for 11-12 minutes, or until the cookies seem set in the center. Let the cookies cool on the sheet for 10 minutes, then place on a wire rack to finish cooling.
While the cookies bake and cool, make the buttercream frosting. Mix the butter on a medium speed in a large bowl for 30 seconds, or until smooth.
Add the vanilla extract and salt. Mix on a medium speed until combined.
Mix in the powdered sugar and milk on a low speed. Scrape the sides and bottom of the bowl as needed with a rubber spatula.
Once the powdered sugar is incorporated, mix for an additional minute on a low speed to give the frosting a super smooth consistency.
Spread a thin layer of frosting on top of the cooled cookies using a small offset spatula or butter knife. Top with sprinkles, then enjoy!
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Notes
Tips for Making the Best Frosted Gingerbread Cookies
Use a cookie scoop to make sure your cookies are uniformly sized.
Space your cookies about 2 inches apart before baking them. They will spread as they bake.
Don't over-bake your cookies! It's hard to see when they start to brown, so keep an eye on the texture of the top of the cookie. Even if they seem a bit soft coming out of the oven, they will continue to bake and set on the tray once they're out of the oven.
Making These Cookies in Advance and Storing Them
This cookie dough can be made up to 2 days in advance. Store it in the fridge in an airtight container, then when you're ready to bake them, let the dough thaw to room temperature, scoop the cookies, and bake them.Baked and frosted cookies can be stored in an airtight container or ziplock bag at room temperature for up to 2 days, in the fridge for 5 days, or in the freezer for a month.You can also freeze baked, unfrosted cookies for up to a month. I like to thaw them in the fridge overnight, then fill them with frosting once they've reached room temperature and are ready to be eaten.