Preheat your oven to 375 degrees Fahrenheit. Spray a 10-inch cast-iron skillet with baking spray and set aside.
In a large mixing bowl, whisk together melted butter, brown sugar, vanilla, and eggs until combined.
In a separate medium mixing bowl, whisk together flour, baking powder, and salt. Add flour mixture to the bowl with the butter mixture and combine mix with a rubber spatula until just combined and no more dry flour is visible.
Fold in crushed peppermint and dark chocolate chunks until mixed into the batter. Pour blondie batter into the prepared cast-iron skillet and smooth out into an even layer.
Bake blondie in the preheated oven for 25-30 minutes until the edges are set and the center is still gooey. The center will look slightly underbaked. Cool in the skillet for 10-15 minutes.
While the blondie is cooling, add powdered sugar, peppermint extract, and two tablespoons of heavy cream to a medium mixing bowl. Whisk together until combined. Add more heavy cream as needed until glaze is smooth and able to be drizzled easily with a spoon.
Drizzle glaze over warm blondie and top with more crushed candy canes if desired. Enjoy!