Cream together with an electric hand mixer for 2–3 minutes, until light, fluffy, and well combined.
Add the egg and egg yolk, and mix again until the mixture is smooth and creamy.
Add the flour, cornstarch, and baking soda, and mix on low speed just until the dough is almost combined.
Fold in the chocolate chunks and chopped pistachios until evenly distributed, making sure not to overmix.
Cover the bowl with plastic wrap and chill the dough for at least 1 hour—I prefer chilling it overnight for the best texture and flavor.
Use a large cookie scoop (or about 3 tablespoons of dough) to portion the cookies and place the dough balls on a parchment-lined baking sheet.
Bake in a 180°C (350°F) preheated oven for 10–12 minutes, then immediately top with extra chocolate chunks.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Line your sheet pan with parchment paper or a silicone mat! This step helps the cookies bake evenly and ensures they release easily from the pan.
Use room-temperature ingredients – Soft butter, eggs blend more easily, creating a smoother dough and better texture.
Don’t flatten the cookies. Leave the dough balls tall so they stay thick and soft while baking.
Measure your flour correctly. Too much flour makes cookies dry and puffy. Spoon and level, or use a kitchen scale for accuracy.
Toast the pistachios. Lightly toasting them brings out their natural flavor and adds extra crunch.
Use a cookie scoop. Scooping the dough with a cookie scoop helps the cookies bake evenly and stay the same size.
Chill the dough. Chilling for at least an hour helps the cookies hold their shape, prevents overspreading, and improves flavor.
Don’t overmix the dough. Once the flour is added, mix only until combined to keep the cookies soft and tender.
Underbake for a chewy center. Pull the cookies out when the edges are set, but the centers still look soft; they’ll continue setting as they cool.
Use high-quality chocolate. Chocolate chips or chopped bars (55–70%) create the best melty pockets and rich flavor.
Add extra chocolate on top. Press a few chocolate chunks onto each cookie as soon as they come out of the oven for a prettier and more chocolatey result.
Let them cool slightly before moving. They’re delicate right out of the oven, so give them a few minutes before transferring.