In a heatproof bowl, combine the 2 large egg yolks, 1 whole large egg, and ⅓ cup granulated sugar. Whisk together until blended. Place the bowl over a saucepan of simmering water, ensuring the bowl does not touch the water. Continuously whisk the mixture as it cooks until it thickens and feels hot to the touch, about 10 minutes. Remove from heat and let cool to room temperature. In a separate large bowl or stand mixer, whip ¾ cup heavy cream to stiff peaks, then refrigerate until ready to use. In another bowl, mash ½ lb mascarpone cheese until smooth. Gradually whisk the cooled egg mixture into the mascarpone until fully combined, being careful not to overwhisk to avoid a runny texture. Add 1 tablespoon pumpkin spice flavoring and ½ cup pumpkin purée, mixing until incorporated. Finally, gently fold the whipped cream into the mascarpone mixture until smooth and well combined.

In a wide, shallow dish, mix together 1 cup strong brewed coffee or espresso, 2 tablespoons granulated sugar, and ¼ teaspoon pumpkin spice flavor until the sugar dissolves. Dip ladyfingers one at a time into the coffee mixture and arrange a single layer in your serving dish. Spread half of the pumpkin mascarpone filling evenly over the ladyfingers, reaching the edges. Repeat with another layer of soaked ladyfingers, then top with the remaining filling, smoothing the surface. Cover and refrigerate the tiramisu for at least 8 hours or overnight to allow it to set properly. Before serving, cut mini pumpkin shapes from parchment paper and place them on top of the tiramisu. Dust generously with 2 tablespoons cocoa powder and a pinch of pumpkin spice seasoning. Carefully lift the parchment pumpkin cutouts using a toothpick to reveal pumpkin-shaped patterns beneath. Serve by scooping or slicing.