Preheat oven to 350 degrees F. Lightly grease a 9-inch x 13-inch baking dish and set aside.
In a large bowl, beat butter and sugar together until light and fluffy, about 2 minutes. Mix in eggs, vanilla extract, and pumpkin until combined.
In a medium mixing bowl, stir together flour, baking soda, cinnamon, nutmeg, and salt. Slowly incorporate the dry ingredients into the batter, scraping the sides of the bowl and as needed.
Spread about 2/3 of the batter into the prepared pan in an even layer. Sprinkle chocolate chips and walnuts (if using) over the blondie batter.
Place caramels and cream into a heat-proof bowl. Microwave on high for 20 seconds and then stir. Repeat until the caramels are completely melted and the mixture is smooth. Pour melted caramel over chocolate and nuts. Spread around evenly with a butter knife or spoon.
Place dollops of the remaining blondie batter over the top of the caramel layer. Spread those dollops out to try and get a smooth layer of batter over top. It’s fine if some of the caramel layer is peeking through.
Bake for 20 to 25 minutes or until edges are golden and a toothpick comes out clean when inserted into the blondies. It might come out with a little caramel on it which is fine.
Remove from the oven and cool completely before serving. Top with vanilla ice cream or whipped cream if desired.