Preheat oven to 350 and grease an 8x8 inch baking dish. In a large bowl cream together melted butter and brown sugar. Add vanilla and eggs and mix well.
In a medium bowl whisk flour, baking powder, baking soda, and salt. Add dry ingredients to wet ingredients and mix until combined. Stir in nuts and chocolate chips. Spread into prepared dish and bake for 20-30 minutes until a toothpick inserted into the middle comes out mostly clean.
While the blondies are baking, prepare the sauce. Combine butter, sugar, cream cheese, maple syrup, and brown sugar in a medium sauce pan and stir over medium heat until cream cheese and sugars are melted. Simmer for 10-15 minutes until ready to serve. (If needed, thin out with a bit of milk or heavy cream)
Serve blondies warm and top with ice cream and cream sauce. Optional: sprinkle with chopped walnuts or pecans.