In a small mixing bowl, combine the melted unsalted butter, brown sugar, cinnamon, and flour.
¼ cup unsalted butter, ⅓ cup brown sugar, ⅓ cup all purpose flour, ¾ teaspoon cinnamon
Mix everything together with a fork or spatula until fully combined into a smooth, spreadable paste. Set aside.
For the blondies
Preheat your oven to 350°F (177°C). Grease and line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
In a medium saucepan over medium heat, brown the butter. Melt it completely, then continue cooking, stirring occasionally, until it foams and turns golden brown with a nutty aroma. Remove from heat and cool for 10 minutes.
¾ cup unsalted butter
In a large mixing bowl, whisk together the browned butter, brown sugar, and granulated sugar until well combined.
½ cup packed light or dark brown sugar, ½ cup granulated sugar
Add the molasses, egg, egg yolk, and vanilla extract, whisking until the mixture is smooth and creamy.
⅓ cup unsulphured or dark molasses, 1 large egg, 1 large egg yolk, 1 teaspoon pure vanilla extract
Fold in the flour, baking soda, ginger, cinnamon, cloves, black pepper, and salt using a rubber spatula. Mix until just combined; the batter will be thick. Avoid overmixing.
2 and ¼ cups all-purpose flour, 1 and ½ teaspoons baking soda, 2 teaspoons ground ginger, 1 teaspoon ground cinnamon, ¼ teaspoon ground cloves, small pinch of ground black pepper, ¼ teaspoon salt
Spread the batter evenly into the prepared pan, smoothing the top with a spatula.
Sprinkle the cinnamon filling evenly over the batter and gently press it into the dough.
Bake for 25–27 minutes, or until the edges are set. For a gooey texture, pull them out at 25 minutes.
Cool completely in the pan on a wire rack for 1 hour. Use the parchment overhang to lift the blondies out of the pan.
Make the Cream Cheese Frosting:
In the bowl of a stand mixer fitted with the paddle attachment, beat the softened cream cheese on medium speed until smooth and creamy.
½ cup unsalted butter room temperature
Scrape down the sides of the bowl, then add the butter. Beat on medium-high speed for 1 minute.
4 tablespoon cream cheese room temperature
Add the powdered sugar, vanilla, cinnamon, and salt. Mix on low speed until incorporated, then increase to medium-high and beat for 2 minutes.
3 cups powder sugar, 1 teaspoon vanilla extract, 1 teaspoon ground cinnamon, pinch of salt
Adjust the consistency as needed: If too thin, add more powdered sugar; if too thick, add a splash of heavy cream.
Assemble:
Once the blondies are completely cool, spread the cream cheese frosting evenly over the top using an offset spatula.