Preheat oven to 350ºF degrees. Line six 6-inch round cake pans* with parchment paper and coat with nonstick cooking spray.

In a mixing bowl, whisk together the flour, baking powder, baking soda, and salt until combined; set aside.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium speed until lightened and creamy. Beat in the egg whites, one at a time, until combined, scraping down the sides and bottom of the bowl as needed. Beat in the Greek yogurt, vanilla, and almond extract on medium speed.

Pour the dry ingredients into the wet ingredients and mix until combined. Add the Bailey's Irish Cream, then mix until just combined, scraping down the sides and bottom of the bowl as needed.

Divide the batter evenly among six separate bowls, then tint with the green food coloring until you have six different shades of green. Pour the batter into their own separate cake pan. Bake for 14-16 minutes, or until cake springs back when you gently press it. Allow to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.

In the bowl of a stand mixer fitted with the paddle attachment, mix the egg whites, powdered sugar, and salt together until combined. Scrape down the sides of the bowl, then continue beating on medium speed until mixture has thickened and starts to resemble a thinned out marshmallow fluff, about 5 minutes.

Once thickened, reduce mixing speed to medium-low and begin to add the softened butter, 1-2 Tablespoons at a time. Once all the butter has been mixed in, turn the mixer off and scrape down the sides of the bowl. Stir in the vanilla and Bailey's Irish Cream, then beat the buttercream on medium speed until smooth and creamy, about 8-10 minutes.**

In a medium microwave-safe bowl, heat the cream in the microwave until simmering. Remove from the microwave, add the chocolate, shake gently to assure the chocolate is covered in the hot cream, then cover with plastic wrap. Let sit for 5 minutes, remove plastic wrap, then stir until smooth. Tint ganache with green food coloring. Set aside to cool and thicken.

Place the darkest (greenest) cake layer onto a cake plate/pedestal and frost with a layer of buttercream. Top with the next darkest (greenest) cake layer, and frost with buttercream. Keep repeating these steps until you've stacked all of the cake layers. Frost the top and sides of the cake.

If you plan on using sprinkles, add the bottom border of sprinkles first by pressing handfuls of it on with your hand. Slowly pour the ganache over the top of the cake, allowing some of it to drip down the sides. Top with more sprinkles, if desired. Cut, serve, and enjoy!