In a small bowl, combine the 3 tablespoons of instant espresso powder with 1 cup of hot water. Stir until fully dissolved and set aside to cool.
In a large mixing bowl, combine 8 ounces of whipped cream cheese, ½ cup of sugar, and 1 teaspoon of vanilla extract. Beat with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes.
In another bowl, pour in 1 ½ cups of heavy cream and add ⅓ cup of sugar. Using the electric mixer, beat on medium-high speed until soft peaks form, about 3-5 minutes.
Gently fold the whipped cream into the cream cheese mixture using a spatula.
Dip each Twinkie into the cooled espresso mixture briefly. Lay half of the dipped Twinkies in a single layer at the bottom of your 9x13-inch baking dish. Spread half of the cream cheese mixture over the Twinkies. Repeat with the remaining Twinkies and cream cheese mixture.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight.
Just before serving, shave the 3 ounces of semi-sweet chocolate on top of your Twinkie Tiramisu.