01 -
Preheat oven to 175°C. Line a 23×33 cm baking dish with parchment paper for easier removal of bars.
02 -
Using a stand or hand mixer, beat softened butter and dark brown sugar on medium speed until light and fluffy, about 2–3 minutes.
03 -
Add flour, chocolate chips, instant coffee granules, baking powder, salt, vanilla extract, and espresso powder (if using). Mix on medium speed until combined; mixture may appear crumbly, but holds together when pressed between fingertips.
04 -
Transfer dough to prepared pan. Press cookie mixture evenly into base using clean hands, the back of a measuring cup, or a rubber spatula to form an even layer.
05 -
Bake for 20 minutes until lightly golden.
06 -
While the cookie base bakes, combine condensed milk and butter in a small saucepan over low heat. Stir occasionally for about 5 minutes until smooth. Remove from heat and stir in vanilla extract.
07 -
Pour the warm condensed milk mixture over the baked cookie base in an even layer. Return to oven for 10–15 minutes, until topping is bubbling and just golden around the edges.
08 -
Remove pan from oven and sprinkle evenly with flaky sea salt. Let cool for 30–60 minutes, or until the topping is set. Speed cooling by placing in fridge or freezer if desired.
09 -
Once completely cool, cut into bars. Store chilled in an airtight container. Flavour develops further after one or two days.