Gingerbread Ermine Frosting
- While the brownies are cooling, begin making the ermine frosting. In a medium saucepan over medium heat, whisk together the whole milk and flour until smooth. Whisk constantly as the mixture heats to avoid lumps and sticking to the bottom of the pan.
- Continue cooking the milk-flour mixture, whisking constantly, for 3-5 minutes. The mixture should thicken significantly and resemble a very thick pudding or roux. It should coat the back of a spoon without dripping. If there are any lumps, pass it through a fine mesh sieve before cooling.
- Remove the pan from the heat and transfer the thickened mixture to a heat-safe bowl. Immediately press a piece of plastic wrap directly onto the surface of the mixture to prevent a skin from forming. Let it cool completely to room temperature before proceeding—this is important to ensure the frosting emulsifies properly.
- In the bowl of a stand mixer fitted with the paddle attachment, beat the room-temperature butter and packed brown sugar together on medium speed for 2-3 minutes, or until lightened in color and fluffy. Scrape down the sides of the bowl as needed to ensure even mixing.
- Add the completely cooled milk-flour mixture along with the gingerbread spice mix. Beat on medium-high speed for another 2-3 minutes until the frosting becomes smooth, fluffy, and light in texture. Scrape the bowl again to incorporate everything evenly.
- Switch to the whisk attachment and pour in the vanilla extract. Whip the frosting on high speed for 7-8 minutes. This extended whipping incorporates air for a light, cloud-like finish and ensures a perfectly smooth, creamy texture without graininess.
- Once the brownies are fully cooled, use an offset spatula or the back of a spoon to spread the frosting generously over the surface. Create swirls or smooth it flat, depending on your desired presentation.
- Slice the frosted brownies into squares or bars using a sharp knife. For cleaner cuts, wipe the blade between slices. Serve immediately or store as outlined below.
Storage and Serving Tips
These brownies can be made a day in advance and stored in an airtight container at room temperature for up to 2 days or in the refrigerator for up to 5 days. Let chilled brownies come to room temperature before serving for the best texture. The frosting will remain stable and creamy but may firm up slightly when cold. For longer storage, the unfrosted brownies can be frozen for up to 2 months; thaw before frosting and serving.
