Line a metal 9x9 baking pan with parchment paper. Preheat the oven to 350 F/180 C.
Whisk together the flour, sugar, salt, baking powder, baking soda, and spices.
Whisk together the melted butter, sour cream, eggs, oil, milk, molasses, and vanilla extract.
Whisk the dries into the wets until just combined. It’s ok if the batter has some clumps!
Then fold in the hot water until just combined.
Pour the cake batter into the prepared cake pan and bake for 30-40 minutes, or until a toothpick inserted into the center comes out clean. Let the pan cool on a wire cooling rack for 30 minutes, then carefully lift up the parchment paper to remove it from the pan and let it cool completely on the rack.
Cream the butter until smooth, then mix in the powdered sugar on low speed. Once combined, increase the speed to medium and beat for 2-3 minutes until the buttercream is light and fluffy. Mix in the molasses, heavy cream, vanilla extract, and salt and mix until combined.
Spoon the frosting on top of the cooled cake, using the back of a spoon to create swoops and swirls in the frosting. Garnish with mini gingerbread men cookies, sprinkles, sugared cranberries, etc. Cut into 16 servings and enjoy!
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Notes
*Measure your flour properly. This is my #1 baking tip! Do not ever scoop a measuring cup into your flour as this always leads to using too much flour. Instead, use the spoon-level method. This means fluffing the flour first, then spooning it into your measuring cup/spoon. For the BEST results, use a kitchen scale!*