Caramel Pumpkin Spice Latte Cake

Moist brown butter pumpkin spice cake layered with coffee mascarpone whipped cream and salted caramel sauce.

Before starting the cake, mix the 300g of heavy whipping cream and 45g of coffee grounds together. Store the mixture in the fridge until you're ready to make the mascarpone cream. [Alternatively, you can mix in 1 tbsp. of instant espresso powder & set it aside in the fridge.]
Add the butter to a small saucepan and set it over medium heat. Stir the butter occasionally until it turns amber in color and develops little brown specks, then remove it from the heat. Transfer the butter to a medium sized mixing bowl, then set it in the freezer for 5 minutes to cool down.
Preheat the oven to 350°F / 175°C. Butter a 7" springform pan, then coat the inside with sugar.
Once the butter has cooled down a bit, add in the sugars, pumpkin puree, eggs, vanilla, and sour cream. Whisk vigorously until well combined.
Add in the flour, baking powder, salt, and pumpkin pie spice. Fold the dry ingredients into the wet, just until no flour streaks remain.
Pour the cake batter into your prepared pan. Bake for 35-45 minutes, until a toothpick inserted in the center of the cake comes out with only a few moist crumbs.

Once the cake has cooled to room temperature, make the cream filling. In a medium-sized mixing bowl with a hand mixer or stand mixer, beat together the mascarpone and sugar just until the mixture is cohesive.
Place a fine mesh sieve over the bowl, then pour the heavy cream & coffee mixture through the fine mesh sieve.
Beat the mixture until soft peaks form.

Once the cake has completely cooled to room temperature, carefully slice the cake twice horizontally to get 3 even layers
Place the bottom half of the cake back into the springform pan, then spread 1/3 of the mascarpone cream on to the bottom cake layer, along with ¼ c. of salted caramel sauce.
Place the middle cake layer on top, then spread ½ of the remaining mascarpone cream on to the cake, along with the remaining ¼ c. of salted caramel sauce.
Place the top cake layer on top, pushing it down slightly to secure it. Cover the cake with plastic wrap and leave it in the fridge to set for at least 10 minutes.
(Optional) If you'd like to make mini pumpkins on top you will need two piping bags, a 4B piping tip, orange food dye, and cocoa powder. Add ~3 tbsp. of frosting to a small bowl and dye it with orange food dye. Add ~1 tbsp. of cream to another small bowl and dye it with a tiny bit of cocoa powder. The cream may thicken up significantly because of the additional mixing - if this happens, you can thin it out with a little bit of heavy cream to get it back to the same consistency it was before.
Once the cake has set, top it with the remaining mascarpone cream. Transfer the orange cream to a piping bag fitted with a 4B tip, and the brown cream to a piping bag with the tip cut off. Pipe little orange pumpkins on top, then top them with a little brown stem. Slice, serve, and enjoy!