Preheat your oven to 350°F (175°C). In a large mixing bowl, beat the cream cheese until creamy, then add sugar and flour until well combined. Mix in vanilla, cinnamon, heavy whipping cream, and eggs until smooth. Pour this mixture into a prepared springform pan and bake for 40 minutes at 350°F, then reduce the temperature to 200°F and bake for an additional 30-40 minutes, or until the center slightly jiggles. Cool and refrigerate overnight.

Preheat your oven again to 350°F (175°C). In another mixing bowl, cream the softened butter and brown sugar until fluffy. Beat in the vegetable oil, egg, and vanilla extract, mixing well. Gradually incorporate the flour mixture along with the milk until combined. Pour the batter into a greased cake pan and bake for 25-30 minutes, or until a toothpick comes out clean. Let it cool in the pan, then refrigerate overnight to firm up.

In a medium bowl, beat the softened unsalted butter with an electric mixer until fluffy and pale, about 2-3 minutes. Gradually add powdered sugar, mixing between each addition until fully combined and smooth. Pour in the vanilla extract and heavy whipping cream, continuing to beat until you achieve a light and airy frosting consistency. Set the buttercream aside at room temperature while you prepare to assemble your Thanksgiving Piecaken.

Carefully remove the cheesecake and spice cake layers from their pans. Trim both layers to ensure they are even and the same diameter for stacking. Place the cheesecake layer on a cake stand and spread a layer of buttercream frosting on top. Add the spice cake layer directly on top, then frost the top of that layer as well. Take the store-bought (or homemade) pumpkin pie, trim it to fit, and place it on top of the spice cake, ensuring a stable base.

Using the remaining buttercream, frost the entire exterior of the piecaken, smoothing out any imperfections. If desired, you can create decorative swirls or peaks for a beautiful finish. Chill the assembled piecaken in the refrigerator for about 30 minutes to set the frosting. This helps ensure a cleaner cut when serving and enhances the flavors of the Thanksgiving Piecaken.

Once the frosting has set, remove the piecaken from the refrigerator. Use any leftover frosting for decorative touches, and if you'd like, sprinkle with ground cinnamon for an extra holiday flair. When ready to serve, slice carefully to reveal the gorgeous layered structure of your Thanksgiving Piecaken.