Beat cream cheese and sugars in a bowl with a mixer on medium speed until smooth. Then beat in pumpkin, half-and-half, salt, pumpkin pie spice, and vanilla until smooth and fluffy.
Lay enough graham crackers in a 9- by 9-in. pan to cover bottom (cut to fit if necessary). Spread a quarter of pumpkin mixture over crackers with an offset spatula. Layer 3 more times, ending with pumpkin mixture.
Cover; chill overnight. Set leaf cutouts (trace them on paper) on top and dust with cocoa, then remove. (Or, use the cut-out sheet of paper for a reverse stencil, which is easier to handle than individual cutouts.) Cut cake into squares.
Note: Nutritional analysis is per square.