Pre-heat the oven to 350°F (177°C). Prepare regular-sized cupcake tins with paper liners. Set aside.
In a medium mixing bowl, combine flour, baking powder and salt. Set aside.
In the bowl of an electric mixer with the paddle attachment, beat the butter on medium speed until light and fluffy, about 30 seconds. Beat in the sugar gradually, then cream the butter and sugar together for 2 minutes. Add the eggs one at a time, beating well after each one.
Divide the batter evenly into the cupcake cups. Bake for 17 to 22 minutes or until a toothpick or cake tester comes out clean.
Cool for 5 minutes, then remove from the pans and transfer to a wire rack to cool completely.
Make the frosting.
In a large bowl, beat the powdered sugar, butter, salt and spices together. Add milk 1 tablespoon at a time until smooth. Frost the cupcakes.
Make the trees.
Line a baking sheet with parchment paper. Melt the white chocolate in a double boiler or in the microwave. (Be careful — white chocolate burns ever-so-quickly!) Dip the pretzel sticks in white chocolate leaving ½-inch of pretzel at the bottom. Place the pretzels 4 inches apart on the lined baking sheet.
Fill a piping bag with the remaining white chocolate. Use a small round tip. Pipe the white chocolate in a zig-zag pattern perpendicularly across the pretzels, increasing in size from the top to the bottom of the white chocolate-covering. Add sprinkles. Place baking sheet in the fridge for 30 minutes to let the chocolate harden. Place on top of cupcakes.