Preheat oven to 350 degrees.
Line a 9 x 13 baking pan with aluminum foil, pressing the foil into the edges of the pan with extra overhanging on the handles.
Lightly butter the foil.
In a glass dish, use a microwave to melt the butter.
In a large bowl with an electric mixer, beat the melted butter with the brown sugar for about a minute.
Add the eggs and vanilla and beat until well combined and light in color.
Add the gluten free flour and salt and beat until just combined.
Fold in the toffee bits and chocolate chips.
Pour the batter into the pan.
Bake for 25 minutes, checking often towards the end of baking time. The blondies will be golden brown on the edges, yet still soft in the middle. Use a toothpick to check the center, but don't over bake!
Allow the pan to cool completely, then lift the foil edges out of the pan.
Cut into squares and enjoy!