Guinness Brownies

Gather all ingredients.

Preheat the oven to 350 degrees F (175 degrees C). Spray a 9x9-inch square baking pan with cooking spray and line with parchment paper, leaving a 2-inch overhang on one side.  

Heat Guinness in a medium saucepan over high heat until boiling. Skim any foam from the top. Reduce to a simmer over medium-low heat and cook until liquid has reduced to 1/2 cup, 12 to 15 minutes. Transfer to a heatproof bowl or container. Set aside.

Heat butter in the same saucepan over medium heat until melted, about 4 minutes. Add sugar and cook, whisking constantly, until mixture is thickened and sugar is mostly dissolved, about 2 minutes.

Remove from heat, add chocolate, and whisk together until smooth, about 1 minute. (Mixture will be slightly grainy.) Gradually add reduced Guinness, whisking constantly, until batter is glossy and dark, about 2 minutes.

Transfer chocolate mixture to a large bowl, cool slightly, stirring occasionally, about 10 minutes. Add eggs slowly, stirring to combine after each egg, about 30 seconds. Add vanilla, stirring until combined, about 30 seconds.

Combine flour and salt in a medium bowl and whisk together. In two batches, gently stir flour mixture into chocolate mixture until just combined or until no clumps remain, about 1 minute. Pour batter evenly into the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 25 to 30 minutes. Remove from the oven and let cool completely, about 1 hour. When cool, remove from pan and place on a cutting board, slice into squares and serve. Store in the refrigerator in an airtight container for up to one week.