01 -
Preheat oven to 350°F (175°C). Line an 8-inch square baking dish with parchment paper.
02 -
In a large bowl, whisk together the melted butter and brown sugar until smooth and free of lumps. Add the egg and whisk until thoroughly combined, then add vanilla extract and salt, whisking to incorporate.
03 -
Using a rubber spatula, stir in the flour and baking powder until most of the dry ingredients are absorbed. Add the chocolate chips and toffee bits, stirring until no streaks of flour remain.
04 -
Turn the batter into the prepared pan, spreading it into an even layer. The batter will be thick, similar to cookie dough. Sprinkle a pinch of fleur de sel on top.
05 -
Bake for 18 to 20 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs. Allow the blondies to cool completely before cutting and serving.
06 -
Store blondies in an airtight container at room temperature for up to 4 days.