Instructions

Maple Cake Layers:

1. Preheat oven to 350°F. Line four 7 inch pans round pans with parchment rounds, and grease with non-stick cooking spray.
2. Mix together all dry ingredients (flour, baking powder, sugar, and salt) in a stand mixer with a paddle attachment until fully combined.
3. Mix chunks of room-temperature butter slowly into the dry mix, on a low speed. Continue to mix until no large chunks of butter remain, and the mixture becomes crumbly.
4. Pour in egg whites, and mix on low until just incorporated. Mix in the buttermilk in two installments, on a low speed.
5. Add in vanilla extract, maple extract, and oil, and mix at a low speed until fully incorporated. Scrape down the sides of the bowl with a spatula, then beat on low speed for about 15 seconds (the key is to mix until the ingredients are JUST incorporated, so that the batter isn't over mixed). 
6. Divide the batter evenly between four bowls. I like to use a digital kitchen scale to weigh my pans, to make sure the layers are the same height.
7. Use gel food coloring to color one bowl gray, and the rest deepening shades of blue. Mix the color in by hand using a rubber spatula, until the batter is evenly colored.
8. Pour the colored batter in the prepared cake pans.
9. Bake for 34-35 minutes, or until a toothpick comes out clean. Allow the pans to cool for 10 minutes, then run an offset spatula around perimeter of the pan to separate the cake from the pan.
10. Place cake layers into the freezer for 45 minutes, to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans and remove the layers from the pans.
11. Use a serrated knife to level the tops of the layers, and then frost as desired.

Maple Buttercream Frosting:

1. While the cake layers bake and cool, make the vanilla buttercream frosting.
2. Beat the butter on a medium speed for 30 seconds with a paddle attachment, until smooth. Slowly add in the powdered sugar, 1 cup at a time. Alternate with small splashes of cream.
3. Once fully mixed, add in the vanilla extract, maple extract, and salt, and beat on low until the ingredients are fully incorporated, and the desired consistency is reached. 
4. If the frosting is too thick, add in additional cream (1 TBSP at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).
5. If you plan to color the buttercream, add in the gel food coloring once the frosting is fully made, and beat on low until it reaches the desired color

To Assemble The Cake:

1. Stack and frost cake layers on a greaseproof cake board, using a dab of frosting to help stick the first cake layer to the board.
2. Add an even layer of buttercream between each cake layer.
3. Apply a thin coat of frosting around the cake, to fully cover the cake layers. Smooth using a bench scraper, then chill the cake in the fridge (20 minutes) or freezer (5 minutes) until the frosting is firm to the touch.
4. Color 3/4 of the remaining frosting deepening shades of blue, and place each color into its own piping bag.
5. Leave 1/2 cup of frosting uncolored, and place into piping bags.
6. Divide the rest of the frosting between 4 bowls, and color them brown, grey, and two shades of green.
7. For the second layer of frosting, pipe a ring of white buttercream around the base of the cake.
8. Continue to pipe frosting up the cake, starting with your lightest shade of blue, and finishing at the top of the cake with your darkest shade of blue.
9. Smooth using a bench scraper, and chill in the freezer for 10 minutes (until the frosting is firm to the touch)
10. Use a tapered offset spatula to spread some grey frosting in the shape of triangles on the middle of the cake to look like mountains (use a tree cookie cutter as an outline, if needed).
11. Pipe additional white frosting around the base in a slightly wavy line, to add make it look like snow banks. Chill the cake again for 10 minutes in the freezer.
12. Spread white frosting on top of the mountains to give them snowcaps, then pipe trees and bushes on the snow banks using the brown and green frosting.
13. If desired, very carefully pipe white frosting on top of the trees to look like snow.