Preheat the oven to 350°F and line an 8x8-inch baking pan with parchment paper, leaving some overhang for easy removal.
In a medium bowl, whisk together the flour, chocolate protein powder, unflavored protein powder, black cocoa powder, stevia sweetener, and baking powder until well combined and free of lumps.
In a separate bowl, whisk the applesauce, 1/2 cup nonfat Greek yogurt, 1/3 cup almond milk, egg, egg white, and 2 teaspoons vanilla bean paste until smooth and uniform.
Pour the wet mixture into the dry mixture and gently whisk or fold just until no dry streaks remain, being careful not to over-mix.
Pour the batter into the prepared pan and spread it into an even layer.
Bake on the center rack for 24 to 26 minutes, or until a tester inserted in the center comes out clean and the top springs back lightly to the touch.
Cool the cake in the pan for 10 minutes, then lift it out using the parchment and transfer to a wire rack to cool completely.
Once the cake is fully cooled, cut it into strips or rectangles that will fit in two layers inside the 8x8-inch pan; set aside.
In a large bowl, beat the reduced-fat cream cheese with an electric mixer on medium speed for about 1 minute, until smooth and creamy.
Add 1 cup nonfat Greek yogurt and 2 tablespoons almond milk to the cream cheese and beat again until smooth and combined.
Add the vanilla protein powder and beat, scraping down the sides of the bowl as needed, until the mixture is thick, smooth, and spreadable.
Pour the cooled coffee into a large shallow dish.
Place a clean 8x8-inch pan (or the original pan, wiped clean) on the counter and quickly dip each cake strip into the coffee, coating all sides without soaking so long that it falls apart.
Arrange a full layer of coffee-dipped cake strips over the bottom of the pan, trimming pieces as needed to cover the base completely.
Spread half of the cream mixture evenly over the first layer of cake, smoothing the top with a spatula.
Dip the remaining cake strips in the coffee and arrange them over the cream to form a second even layer.
Spread the remaining cream mixture over the second cake layer, smoothing the top.
Cover the pan tightly with plastic wrap and refrigerate for at least 6 hours or overnight until fully chilled and set.
Just before serving, sift the unsweetened cocoa powder evenly over the top of the tiramisu.
Crush the Oreo Thins into small pieces and sprinkle them evenly over the cocoa-dusted surface, then slice into 12 pieces and serve chilled.