Start by creaming the softened butter with the packed brown sugar using a mixer until the mixture is light and fluffy. Blend in the vanilla extract and salt, ensuring everything is well incorporated.
Gradually add the flour to the bowl. At this stage, the mixture will appear crumbly, which is perfectly normal.
Next, pour in 2 tablespoons of milk, mixing until the dough achieves a soft and familiar cookie dough consistency.
Gently fold in the mini chocolate chips and milk chocolate chips, distributing them evenly throughout the dough.
Transfer any leftovers to an airtight container and store them in the refrigerator. For longer storage, freeze the dough for up to three months, ensuring it remains fresh and ready to enjoy.