Preheat oven to 350 degrees F. Grease and flour three cake pans and line the bottoms with parchment rounds.
Whisk the cake flour, baking powder, and salt in a medium bowl. Set aside.
In a stand mixer, beat the butter, oil, and sugar on medium speed for 3 minutes until light and fluffy.
Add egg whites in two additions, mixing until just combined after each.
Mix in the vanilla and almond extracts.
With the mixer on low, add the flour mixture in three additions, alternating with the buttermilk in two additions, starting and ending with flour. Mix just until combined.
Immediately fold in the jimmies using a spatula and as few strokes as possible.
Divide the batter evenly among the three pans and bake right away for 22 to 26 minutes, until a toothpick comes out clean.
Cool in the pans for 10 minutes, then transfer to a wire rack to cool completely before frosting.
Beat the butter alone for 2 minutes until pale and creamy. Add powdered sugar one cup at a time, alternating with the heavy cream. Add vanilla and salt, then beat on high for 2 minutes until fluffy.
Frost between each layer, apply a thin crumb coat, refrigerate for 20 minutes, then apply the final coat of frosting and press jimmies onto the sides and top.