1: Preheat oven to 375-degrees. Melt butter in a heavy-bottom medium saucepan over low heat. Sift together the flour, salt, and baking soda and set aside. Pour the melted butter in the mixer's bowl. Add the sugar and brown sugar. Cream the butter and sugars on medium speed. Add the egg, yolk, milk, and vanilla and mix until well combined.
2: Slowly incorporate flour mixture. Fold in chocolate chips. Chill the dough, then scoop onto parchment-lined baking sheets using a #20 ice cream scooper; 6 cookies per sheet. Bake for 14 minutes, or until golden brown, checking the cookies after 5 minutes. Rotate the baking sheet for even browning.
3: This is the best recipe I have used for making cookies that are nice and chewy. The secret is the use of an egg and an egg yolk; also, chilling the dough is important.