01 -
Set the oven to 175°C and line a baking sheet with parchment paper or a silicone mat.
02 -
Combine unsweetened chocolate, semi-sweet chocolate bar, and butter in a microwave-safe bowl. Heat in 15-20 second intervals, stirring each time until fully melted and smooth. Alternatively, melt using a double boiler over moderate heat, whisking until smooth.
03 -
Sift together the flour, baking powder, and salt in a small bowl. Set aside.
04 -
In a large bowl, use a mixer fitted with a paddle attachment to beat eggs, sugar, espresso powder, and vanilla extract on medium-high speed for 1 to 2 minutes until well combined and slightly fluffy.
05 -
Reduce mixer speed to low and gradually add the melted chocolate mixture, followed by the sifted dry ingredients. Scrape the sides and bottom of the bowl as needed to ensure thorough blending.
06 -
Fold in the semi-sweet chocolate chips and chopped nuts evenly using a spatula.
07 -
Using a medium-sized cookie scoop or ice cream scoop, drop dough portions onto the prepared baking sheet, spacing them a few centimeters apart.
08 -
Bake in the preheated oven for 10 to 12 minutes until cookie tops are dry but centers remain moist and chewy. Avoid overbaking.
09 -
Let cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely or serve slightly warm.