3/4cup(1 and 1/2 sticks) unsalted buttersoftened to room temperature
1 and 1/2cupsfirmly packed brown sugar
1cups(2 sticks) unsalted buttersoftened to room temperature
1Tablespoonmilk or cream
Place oven rack on the middle setting and preheat the oven to 350ºF. Grease and flour (or use homemade cake release) two 8" or 9" round cake pans.
In a large bowl whisk together the flour, ginger, cinnamon, nutmeg, cloves, allspice, salt, pepper, baking soda, and baking powder. Set aside.
In a large bowl with a handheld mixer, or the bowl of a stand mixer fitted with the paddle attachment, cream the butter and brown sugar together until light and fluffy. Add the eggs one at a time, allowing the first to incorporate before adding the second. Add the molasses and beat again on medium speed until everything is incorporated, scraping down the sides and bottom of the bowl with a spatula as needed.
Add the flour mixture in three additions alternating with the milk, starting and ending with the flour mixture. Mix until smooth.
Divide batter evenly between the two prepared cake pans. Bake cakes for about 26-30 minutes or until a toothpick inserted in the center comes out clean and the tops are nicely puffed. Remove from oven and allow cakes to cool completely on a wire rack before assembling.
In a large bowl with a handheld mixer, or a stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 2 minutes.
With the mixer on low, add in the powdered sugar, molasses, and milk or cream and beat until completely smooth, about 3 minutes. If frosting is too stiff, add more milk. If it is too thin, add more powdered sugar.
ASSEMBLE THE CAKE
Trim cooled cake layers to create a flat surface. You can do this with a large serrated knife or a cake leveler. Cut each layer in half horizontally again if you'd like a more layered cake. Place one layer on a plate or cake stand and cover the top with molasses buttercream frosting. Spread evenly with an offset spatula.
Place second layer on top, cut surface down. For a sturdier cake, refrigerate at this point for about 10 minutes. When cake is slightly chilled, remove from refrigerator and spread more frosting on the top and around the sides. Serve. Leftovers stay fresh, covered tightly, at room temperature up to 5 days and in the refrigerator up to 1 week.
Make ahead: prepare cakes and frosting up to 1 day in advance. Cover cakes tightly and keep at room temperature or in the refrigerator until ready to assemble. Refrigerate prepared frosting in an airtight container until ready to use. Unfrosted cake layers may be frozen, wrapped tightly, up to 2 months. Thaw overnight in the refrigerator before assembling. Frosted cake can be frozen, wrapped tightly, up to 2 months. Thaw overnight in the refrigerator and bring to room temperature before serving.