Preheat your oven to 350 degrees. Oil two 8 inch circular cake pans and line with parchment paper.

Add buttermilk and basil to a nonstick pan. Warm over medium heat until it reaches a simmer. Turn off the heat, and allow milk and basil to cool, preferably overnight in the fridge. Then strain out the basil.

Add sugar, oil, butter, and vanilla to a mixing bowl and combine with a hand mixer. Add buttermilk and mix until combined.

In a separate bowl, whisk together the flour, baking powder, and salt.

Add the dry ingredients to the wet ingredients and mix with a spatula until just combined. 

Add egg whites to another mixing bowl. Whip with a hand mixer on high speed until stiff peaks form. Using a spatula, mix egg whites into batter until just combined. Do not over mix.

Divide batter between pans evenly. Bake for 40 minutes, or until a toothpick inserted into the center comes out clean. 

Remove cake from oven, remove from pans, and allow to cool. 

To make the frosting, combine all of the ingredients with a hand mixer until smooth and creamy. 

Frost the cake with the buttercream, and enjoy!