Instructions

• Preheat oven to 350°F. Line an 8x8-inch baking pan with aluminum foil and spray the foil with cooking spray; set pan aside.
• Make the blondie batter: In a large, microwave-safe bowl, add ½ cup (1 stick) unsalted butter and microwave until melted, about 1 minute. Let the melted butter cool briefly (about 30–60 seconds) so it is not piping hot. Add 1 large egg, 1 cup light brown sugar (packed), and 1 tablespoon vanilla extract; whisk until smooth.
• Add 1 cup all-purpose flour and ½ teaspoon salt to the wet mixture. Stir until just combined—do not overmix. Turn the batter into the prepared pan and smooth the top lightly with a spatula.
• Bake the blondies for about 20 minutes, or until the top is set in the center and a toothpick inserted into the center comes out clean or with a few moist crumbs (no wet batter). Remove from oven and place the pan on a wire rack to cool while you make the glaze.
• Make the glaze: Have all glaze ingredients measured and ready. In a medium saucepan, melt ¼ cup unsalted butter over medium-high heat. Add 1/3 cup light brown sugar and whisk while bringing the mixture to a boil. Allow it to boil rapidly for 1 minute, whisking nearly continuously.
• Remove the pan from the heat and let it cool for about 1 minute. Carefully add 4 tablespoons half-and-half or cream (the mixture will bubble vigorously) and whisk aggressively to incorporate and calm the bubbling.
• After bubbling subsides, whisk in 1 tablespoon vanilla bean paste. Then add 2 cups sifted confectioners’ sugar (must be sifted) and up to ¼ teaspoon salt (optional). Whisk until smooth. If the glaze is too thin, whisk in additional sifted confectioners’ sugar a little at a time until you reach a pourable but not runny consistency. If it is too thick, whisk in a little more half-and-half/cream at a time until pourable.
• Pour the glaze evenly over the cooled blondies in the pan and spread gently if needed. Allow the glaze to set for about 30 minutes before lifting the blondies from the pan using the foil, slicing, and serving.
• Store blondies airtight at room temperature for up to 1 week, or freeze for up to 6 months.