Beat together butter, brown sugar, and egg yolk until combined. You do not want to beat for 1-2 minutes like normal cookies, you just want everything incorporated.
1 cup butter, 1 cup brown sugar, 1 large egg yolk
Add in flour and vanilla. Mix until just combined.
1 cup all-purpose flour, 2 teaspoon vanilla extract
Press into a greased half sheet pan or a 13x9 inch baking dish.
Bake for 20-25 minutes until the edges are golden.
Sprinkle chocolate chips evenly over the bars.
1 12 oz bag milk chocolate chips
Let sit for 5-7 minutes (or return to the oven for 2-3 minutes) until the chocolate is shiny. Gently spread melted chocolate into an even layer.
Sprinkle with toffee bits
1/2 cup toffee bits
Let the chocolate set before slicing into bars
Video
Notes
I have tested this recipe a dozen times, and 1 cup of flour works for me. You need to bake until the bars are golden brown on top, they will be bubbly, with holes all over the top, and not look normal - that is how it is supposed to be. The quality of butter has changed this year (2022) and seems to have a higher water content in the past, so it is affecting a lot of baking recipes. It is best to use a name brand quality butter, as those are leading to the best results. If you use a store brand butter, you will need to add more flour.Follow the Recipe Tips section in the blog post for more tips.If your dough is very sticky, add 1/2 cup of flour. You can add chopped pecans in place of toffee or use both! Recipe very slightly adapted from Glitter and Goulash