For the Chai Syrup:
1 cup water
6 tablespoons sugar
4 bags chai tea
4 cracked cardamom pods
1 cinnamon stick
4 whole cloves
For the cupcakes:
2 1/2 cups all-purpose flour
2 1/2 teaspoons baking powder
3/4 teaspoon salt
1 1/2 teaspoons ground cinnamon
1 teaspoon ground ginger
1/2 teaspoon ground cardamom
1/4 teaspoon ground cloves
1 cup brown sugar
1/2 cup granulated white sugar
3/4 cup + 2 tablespoons grape seed oil
4 large eggs
3 tablespoons Chai Syrup
1 teaspoon vanilla extract
2 cups pureed cooked sweet potato (or a 15-ounce can sweet potato or pumpkin puree), see Recipe Note
For the frosting:
1 cup unsalted butter, softened
3 1/2 to 4 cups powdered sugar
2 tablespoons Chai Syrup, or to taste
1/2 teaspoon vanilla extract
Cinnamon (ground) for dusting the tops
To make the Chai Syrup, combine the water, sugar, cinnamon stick, cloves, and cardamom pods in a medium saucepan. Heat over medium until mixture starts to bubble and sugar dissolves. Add in the tea bags, and simmer over low heat until the mixture has reduced to about 1/3 to 1/2 cup and become syrupy. Removed from heat and discard cinnamon, cardamom, and tea bags. Cool before using.
To make the cupcakes, pre-heat oven to 350°F and line 2 12-cup cupcake tins with liners. Sift together the flour, baking powder, salt, and spices in a small bowl. In the bowl of a stand mixer, combine the sugars and grape seed oil. Using the paddle attachment, mix on medium speed. Turn mixer to low, and add in the eggs, chai syrup, and vanilla. Stop mixer and scrape down the sides and bottom of the bowl. With the mixer on low, add in the dry ingredients in two batches. Mix until just combined. Stir in the pureed sweet potato with a spatula.
Divide mixture between all the wells in the cupcake tins. Do not fill each cupcake liner more than 2/3 full. Bake for 20 to 23 minutes or until a toothpick comes out clean when poked into a cupcake. Rotate the halfway through. Cool completely before frosting.
To make the frosting, place the butter in the bowl of an electric mixer. Using the paddle attachment, mix until smooth. With the mixer on low, gradually add in the remaining ingredients, adding more powdered sugar for a thicker frosting and more Chai Syrup for sweetness and flavor. Once combined to your liking, turn the mixer up to medium and mix for a couple minutes until smooth and fluffy.
To assemble, transfer the frosting to a pastry bag fit