1. Preheat your oven to 350°F. This step is crucial as it ensures that your blondies bake evenly. Line an 8-by-8-inch baking pan with aluminum foil and spray it with cooking spray. This will help prevent sticking and make for easy removal later.
2. In a large, microwave-safe bowl, add the ½ cup unsalted butter and heat it in the microwave until melted, about 1 minute on high power. Be sure to watch it closely so it doesn't bubble over.
3. Once the butter is melted, wait a moment to let it cool a bit before adding the 1 large egg. This prevents the egg from scrambling. Add the egg, 1 cup light brown sugar, and 1 tablespoon vanilla; whisk until the mixture is smooth and incorporated.
4. Next, add 1 cup all-purpose flour and ½ teaspoon salt to the bowl. Stir gently until just combined. Be careful not to overmix as this can make the blondies tough.
5. Now it’s time to fold in the 1 cup white chocolate chips. This is where the magic happens! The chips will melt slightly into the batter, creating pockets of gooey sweetness.
6. Pour the batter into your prepared pan, smoothing the top lightly with a spatula as necessary. This ensures an even bake.
7. Bake in the preheated oven for about 20 to 22 minutes. Keep an eye on them; the top should be set and firm, and a toothpick inserted should come out clean or with a few moist crumbs, but no wet batter.
8. Once baked, remove the pan from the oven and place it on a wire rack to cool completely. This is crucial before frosting.
9. While the blondies are cooling, you can prepare the frosting. In a large bowl, combine 6 ounces cream cheese and ¼ cup unsalted butter. Beat with a handheld electric mixer until smooth and creamy.
10. Add 1 ½ cups confectioners’ sugar, ½ teaspoon vanilla, and ½ teaspoon salt to the bowl. Mix until incorporated and the frosting is smooth and spreadable.
11. Once the blondies have cooled completely, spread the cream cheese frosting evenly over the top.
12. For a finishing touch, sprinkle about ½ cup white chocolate chips and 3 to 4 tablespoons holiday sprinkles over the frosting before slicing into squares and serving.
