In a heat-proof, microwave-safe bowl, add ¾ cup of white chocolate and heat it in the microwave in 15 second intervals - stirring after each round. Once the chocolate is melted, set aside to cool.
In a mixing bowl, add the pumpkin puree and cream cheese and beat until smooth with an electric mixer.
Crush the graham crackers to crumbs using a food processor or by putting them into a ziptop bag and crushing them with a rolling pin.
Add the graham cracker crumbs, powdered sugar, and pumpkin spice to the mixing bowl and mix well.
Pour the melted white chocolate in the mixing bowl.
Mix until all is fully combined.
Cover the bowl with saran wrap and put it into the refrigerator for at least 30 minutes.
Line a baking sheet with parchment paper.
Cover your hands with powdered sugar then scrape out a heaped teaspoon of the mixture from the bowl and roll into a ball using your hands. Set on the baking sheet.
Repeat until all the mixture is used and the balls have been formed.
Put the rolled balls back into the refrigerator while you melt the other chocolate.
Add the 1 cup white chocolate and 4 ounces semi-sweet chocolate to separate microwave-safe bowls.
Melt the chocolate in the microwave in 15 second intervals - stirring after each round.
Dip the truffle balls, one at a time into the melted chocolate.
Sprinkle them with a few graham cracker crumbs if you like. Put the chocolate-covered balls back onto the parchment lined baking sheet to set either at room temperature or in the refrigerator.