1. Preheat your oven to 350°F (175°C) and grease an 8×8-inch baking pan.

2. In a large mixing bowl, combine 1 cup light brown sugar and 1/2 cup melted unsalted butter until smooth.

3. Add in 2 eggs and 1 teaspoon vanilla extract; stir to incorporate.

4. Fold in 1 cup all-purpose flour and 1/4 teaspoon salt just until no dry streaks remain.

5. Pour the batter into the prepared pan and smooth the top.

6. Bake for 22–25 minutes or until the edges are set and a toothpick inserted comes out clean or with moist crumbs.

7. While the bars bake, make the sauce: in a saucepan, melt 1/2 cup butter with 1/2 cup brown sugar over medium heat.

8. Stir in 1/3 cup heavy cream and bring to a gentle boil. Let simmer for 2–3 minutes until slightly thickened, then remove from heat and add 1/2 teaspoon vanilla.

9. Let the bars cool for 5–8 minutes out of the oven, then pour the warm sauce evenly over the surface.

10. Let bars cool completely before slicing for clean edges, or enjoy slightly warm for a gooier texture.