Root Beer Float Layer Cake

all-purpose flour

best-quality Dutch-process dark cocoa powder (see notes)

baking powder

salt

buttermilk, room temperature

root beer (not diet)

unsalted butter, room temperature

packed light brown sugar

eggs, room temperature

mayonnaise, room temperature

baking soda

distilled white vinegar

root beer flavour oil OR 1 1/2 tsps of root beer extract (see notes)

unsalted butter, room temperature

salt

confectioners' sugar, sifted

heavy cream

pure vanilla extract or vanilla bean paste

melted vanilla ice cream (in a pinch, you can use 1/2 cup of half-and-half)

unsalted butter, room temperature

confectioners' sugar, sifted

heavy cream

root beer flavour oil (see notes)

salt

best-quality dark chocolate, chopped or callets/discs (see notes)

best-quality dark chocolate, chopped or callets/discs (see notes)

unsalted butter

light corn syrup

salt

root beer flavour oil or 2 tsp of root beer extract (see notes)

round or scalloped cake board, either 7 or 8" round (optional )

offset palette knife (see notes)

straight palette knife (see notes)

ice cream scoop or large cookie scoop (see notes)