Prep the mini bundt cake pan by spraying it with cooking spray, and then sifting cocoa powder over each section. Set aside.
In a large bowl, whisk together flour, sugar, spices, and salt.
In a separate medium bowl, whisk together melted butter and molasses until well blended. Beat in the eggs. Then beat in the buttermilk and vanilla until all ingredients are well-combined. Gradually mix the wet ingredients in with the dry ingredients, until well blended.
Pour batter into each mini bundt cake section of the pan, almost to the top but leaving a little bit of room as the cake will puff up. I use a cookie/ice cream scoop to easily do the job (each mini bundt cake opening takes about 2 large scoops).
Bake at 350°F for 45 to 50 minutes. Gingerbread bundt cakes are done when a toothpick inserted into one of the cakes comes out clean.
While the cakes are baking, make the icing.
In a large bowl, whisk together confectioner's sugar and lemon juice. Gradually add water, 1 teaspoon at a time, as needed until icing becomes smooth and spreadable. Mix in peppermint extract, if using.
Cook in the pan for 5 to 10 minutes, then flip over onto a cooling rack and decorate with icing and sprinkles. Allow icing to set, about 5 to 10 minutes.
Storage: You can store mini bundt cakes in an airtight container in the fridge for up to 5 days.