In a bowl, mix together root beer schnapps, root beer, and vanilla extract. Set aside.
In a separate bowl, cream together butter and sugar until light and fluffy.
Add eggs, mix until smooth.
Sift in flour, baking soda, baking powder and salt.
Mix with hand mixer on low, while slowly pouring in root beer mixture.
Mix until smooth and lump free.
Pour into lined cupcake pan. (Use foil cupcake liners to avoid leakage later.) Fill nearly to the top, you may think its over-filled, but it puffs up perfectly this way. Don't be tempted to use more than 24 cupcake cups.
Bake for 15- 20 minutes, until golden brown and cake springs back when touched.
While cupcakes are baking, prepare your butter cream and root beer glaze. For glaze, put all ingredients into a bowl and mix with a wisk until smooth and lump free.
To assemble, start by letting cupcakes cool, still in the pan.
While still slightly warm, pour 1 Tbs. of root beer schnapps over each cupcake. Pour on slowly to allow schnapps ( or regular root beer for the kiddies) to soak inches.
Once the schnapps has soaked in and let sit for a few minutes, pour a couple tablespoons of glaze over each cupcake.
When the glaze sets up a bit and isn't too runny, put a "scoop" of buttercream atop each. For an added touch, you can even place a root beer barrel candy on each one.