Preheat oven to 350°F and line an 8x8 baking pan with parchment paper.
In a small bowl, whisk together the flour, baking powder and salt. Set aside.
In a stand mixer with the paddle attachment, beat the butter, brown sugar, and granulated sugar on medium-high speed until light and fluffy, about 2 minutes.
Add egg and vanilla and mix on medium speed until well combined.
Add flour mixture and mix on low speed until just combined. Remove bowl from stand mixer and use a spatula to fold in the toffee bits and chocolate. The batter will be very thick - almost cookie dough-like.
Transfer the batter into the prepared pan and use a spatula to press it evenly to the edges.
Bake for 30-35 minutes, until edges are golden brown.
Let the blondies set in the pan for 10 minutes before using the parchment paper to transfer to a cooing rack.
Wait for the blondies to completely cool before slicing.