In a large mixing bowl, add in your butter, white & brown sugar and cream everything together.
Next add in your eggs and vanilla extract to the mixture and continue mixing everything together.
Now in another bowl, combine your all-purpose flour, salt, cornstarch, baking powder, and Matcha powder.
Sift this mixture over your wet mixture and then mix everything together until you no longer see any white flour on your dough.
If you’re using a large chocolate bar, you will need to chop up the chocolate into smaller pieces. If on the other hand you’re using white chocolate chips then you can skip this step.
Now add in about 75-80% of your white chocolate to the dough and mix everything together.
Take an ice cream scoop and scoop out a large helping of the cookie dough onto a large tray lined with parchment paper. Repeat this for the rest of the dough leaving about 1-2 inches between each cookie, as the cookie will spread out when baked.
Add in the rest of the white chocolate to the top of each cookie then place the cookie dough in the fridge to chill for at least 1 hour.
After 1 hour, take the cookie dough out and bake the cookies in a preheated oven at 350°F or 180°C for about 12 minutes.
Once baked, allow the cookies to cool down before serving.