Preheat oven to 350°. Line a 13×9-inch baking pan with heavy-duty foil.
In a small microwave-safe bowl, heat butter and chocolate in microwave on high in 30-second intervals, stirring between each, until melted and smooth (about 1 to 2 minutes total).
In a large bowl, combine chocolate mixture and sugar. Beat with a mixer at medium speed until well blended. Add eggs, one at a time, beating well after each addition. Add flour, salt, and vanilla, beating until just combined.
Spread batter into prepared pan. Bake for 10 minutes. Sprinkle pecans and toffee bits evenly on top. Bake until a wooden pick inserted in center comes out still slightly sticky, 20 to 25 minutes more.
Let cool completely in pan on wire rack. Using a serrated knife, cut brownie into 24 squares.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/pecan-toffee-brownies-recipe/