For the cupcakes, preheat oven to 350ºF. Line 24 muffin cups with cupcake liners and coat lightly with non-stick cooking spray.
In a small bowl, combine flour, baking powder and salt. Set aside. Using an electric mixer, cream butter and sugar on medium speed until light and fluffy. Beat in egg whites and full egg one at a time, until well combined. Mix in vanilla extract. On low speed, alternate adding flour mixture with the milk and raspberry iced tea, beginning and ending with the flour. Mix just until combined.
Fill cupcake holders halfway with cupcake batter. Place 1 teaspoon of raspberry jam in the middle of the batter and top each cupcake with more batter, filling tin ¾ full. Bake 20-22 minutes, until slightly golden and cooked through. Cool completely before frosting.
For the white chocolate frosting, using an electric mixer, cream together butter and icing sugar on low speed until well combined. Add melted white chocolate and milk, mixing until smooth and desired spreading consistency. Frost cooled cupcakes and drizzle seedless raspberry jam over the frosting, topping with white chocolate curls.