Set the oven to 350°F (175°C). Grease a 9×13-inch pan or line it with parchment paper for easy cleanup.

Whisk melted butter and brown sugar until smooth. Add eggs and vanilla, then mix until fully combined.

Stir in flour, baking powder, and salt. Mix until just combined, being careful not to overmix.

Gently fold in butterscotch chips and toffee bits, making sure they’re evenly spread throughout the dough.

Spread the batter evenly in the pan. Bake for 25–28 minutes, until golden on top and the edges pull away from the sides.

Let the bars cool completely in the pan. For a gooier center, slightly underbake and chill before slicing.