01 -  Preheat oven to 325°F. Grease and line an 8x8-inch baking pan with parchment paper, ensuring an overhang for easy removal. 
 02 -  In a small saucepan, gently warm whole milk and heavy cream together until just heated but not boiling. Set aside. 
 03 -  In a large mixing bowl, beat egg yolks with granulated sugar using an electric mixer or whisk until pale and creamy, approximately 2 minutes. 
 04 -  Whisk in melted and cooled butter, pumpkin purée, and vanilla extract until the mixture is smooth. 
 05 -  Sift in all-purpose flour, salt, and pumpkin pie spice. Mix until just combined. 
 06 -  Gradually whisk in warmed milk and cream until a thin, smooth batter forms. 
 07 -  In a clean mixer bowl, beat egg whites to stiff peaks. 
 08 -  Carefully fold whipped egg whites into the batter in three additions, maintaining a light texture. Mixture may appear slightly curdled; this is expected. 
 09 -  Pour batter into prepared pan. Bake for 50 to 55 minutes, or until the top is golden and center is set but still slightly wobbly. 
 10 -  Allow cake to cool completely in pan. Refrigerate for at least 4 hours or overnight for defined layers. 
 11 -  Lift cake out using parchment overhang. Slice and plate with whipped cream and a dusting of cinnamon or nutmeg as desired.