In a stand mixer add both sugars, oil, pumpkin puree, vanilla, eggs, and sour cream and thoroughly mix until combined.
In another large-sized bowl add the remaining ingredients and whisk to evenly distribute the ingredients.
Add all the dry ingredients at once into the wet batter and mix until just combined.
Line 3-6in rounds with parchment paper and evenly distribute the cake batter.
Bake at 350℉ for 20-25 minutes or until a toothpick is inserted and clean.
Allow the cakes to cool and then wrap the cakes until ready for use.
Browned Butter Cream Cheese Frosting
In a medium-sized saucepan melt the butter on medium heat until it's fully melted.
Once the butter has melted you will begin to hear crackling noises. The butter will start browning around the edges of the pan. Take a heat-safe spatula and mix around the bottom of the pan making sure not to burn the milk fats.
The butter will be a light amber color and the milk solids will just slightly be a brown color, the butter should smell nutty. Take the saucepan off the heat and allow it to cool. Once cooled transfer the browned butter into a bowl and refrigerate to allow the butter to solidify.
In a stand mixer add in the cooled browned butter and whip for 5 minutes until fluffy and light. Add in the softened cream cheese and continue to whip on medium-low speed until mixed and smoothed. Add in the powdered sugar slowly and mix until fluffy and light.
Pumpkin Decor
In a medium bowl pour in the white chocolate chips.
Heat up the heavy cream in a small saucepan and then pour the heavy cream over the chips and cover with saran wrap. After 5 minutes stir the ingredients together. The texture should be thick like dough. If the texture is too watery then let it cool down until it's easier to work with.
Divide the white chocolate dough into 3 small bowls depending on what colors you want your pumpkins.
Place a small amount of gel food coloring and mix the dough really well to get the color all mixed it.
Roll the ball into the desired size of the pumpkin. Try to roll the ball as smooth as you can. Take a toothpick and indent the sides of the pumpkin. Gently push down on the middle of the ball to create a rounder flatter pumpkin look and then place a mini chocolate chip on top to replicate the stem.
This step can be made ahead of time and stored in an airtight container.
Assemble:
Cut and level the top of the cakes.
Add the frosting to a large piping tip or ziploc bag for a cleaner and easier assemlbly.
Begin with a layer of cake on either a large plate or cake stand making sure the cake is cut side up.
Pipe the frosting on the outer edges of the cake and then fill the inside with the caramel filling.
Repeat this step one more time and then place the last layer on top making sure the bottom side of the cake is on the top. This will ensure the cake won't be lopsided.
Refrigerate the cake for at least 30 minutes. This will help firm up the frosting and the caramel to reduce the cake from sliding while frosting.
Once the cake is firm coat the outside of the cake with a thin layer of frosting and then chill the cake again until the frosting has set.
Frost the cake with the remaining buttercream and then place the pumpkins on the cake.