Making the Toffee

1. If making the toffee bits, line a small baking tray with parchment and set to the side. Place a small heavy bottomed saucepan with tall sides over medium low heat and add the butter to melt. Pour in the sugar and salt and whisk continuously for a minute until combined. Continue stirring constantly as the sugar mixture gradually turns more golden brown in color. Eventually, as you continue to stir the sugar mixture, it will start to look like runny peanut butter (if using a candy thermometer, it should reach 295-305F). This process should take about 10 minutes. Before removing from heat, whisk in the vanilla.
2. Being careful, immediately pour the toffee onto the baking tray, allowing it to spread into an even layer (try to work quickly as the toffee will begin to stiffen immediately). Let the toffee fully cool and harden for 15-20 minutes in the fridge. Once it is fully hardened, carefully peel the toffee from the parchment paper and place in a large resealable bag. Use a heavy spoon or rolling pin to carefully tap the toffee and shatter it into smaller bits.

To Make the Brown Butter

1. To brown the butter, place a small saucepan with tall sides over medium low heat then add your butter and allow it to completely melt. Use a spatula to continuously stir the melted butter until it begins to foam. Lower the heat slightly until the foam decreases, continuously stirring until you begin to see the butter start to turn a shade more golden brown in color. You will see tiny brown flecks sinking and accumulating to the bottom of the pan. Remove from the stove top then pour into a large mixing bowl to cool.

Making the Cookies

1. To the bowl with the cooled brown butter, add the light brown sugar, and granulated sugar then use a hand mixer or whisk to mix everything together until combined.
2. Add the yogurt, vanilla, and espresso powder then use the hand mixer or whisk to whip together until smooth.
3. To a separate bowl, combine the flour, baking soda and salt and whisk to combine.
4. Pour the flour mix into the wet ingredients, then use a spatula to scoop the sides of the bowl and fold inward to mix the batter until just about combined.
5. Next, add in the chocolate chips, chopped chocolate, and toffee bits (add more if desired) then fold it into the dough making sure not to over mix. Cover the bowl and place in the fridge for 24 hours to set (if you are in a rush, chill the dough for at least 2 hours so it can firm up before baking).
6. When ready to bake, remove the bowl from the fridge, preheat the oven to 350F and line two half baking trays with parchment paper.
7. Use a large cookie scoop (about 3 tbsp of the cookie dough) to scoop the dough then roll them into balls and place on the tray making sure there is about 2 inches of space between each dough ball. Press a few more chocolate chunks and toffee bits on top of each cookie as desired.
8. Place the tray in the oven for 10-12 minutes until the cookie edges appear golden and the centers still appear slightly underdone.
9. When the cookies are out of the oven, you may notice some cookies aren’t in perfect circles. Fix the edges by placing a cookie cutter overtop of the cookie and moving it in a circular motion to round out the cookie. Allow the cookies to cool on the baking tray for 10 minutes then transfer to a wire cooling rack to completely cool and firm up. Sprinkle with flaky salt and enjoy!