Preheat oven to 375ºF. Grease a standard 12 (2-1/2 inch) well muffin pan or line with paper liners.
Mix together the spices for the Chai Spice Mix in a small bowl and set aside. Whisk together flour, 2 teaspoons of the spice mix, baking soda and salt in a bowl and set aside.
Combine butter, sugar and vanilla in a large mixer bowl and beat on medium speed for 1 to 2 minutes or until pale and fluffy. Add eggs one at a time beating well after each addition. Continue mixing and add the flour mixture and buttermilk alternately until well blended.
Portion batter into baking cups filling each two-thirds full. Bake for 20 to 25 minutes or until a wooden pick inserted in the center comes out clean. Remove from oven and transfer to a cooling rack. Cool to room temperature prior to frosting.
To make frosting:
Beat butter with an electric mixer on medium high speed for 1 to 2 minutes until pale and fluffy. Gradually add powdered sugar. Add the spice mix and vanilla and continue beating until smooth.