Preheat the oven to 350 degrees F. Line cookie sheets with parchment paper. Cream butter and sugars together. Beat in eggs, milk, vanilla and pistachio oil. Combine flour, baking soda, baking powder and salt. Process the oats in a food processor, leaving some texture to them and add to flour. Gradually add flour mixture to butter mixture. Stir in nuts and white chocolate chunks. *Drop mixture by heaping teaspoons onto baking sheets, allowing for spreading. Bake 8 to 10 minutes or until golden brown. Let cool slightly on the baking sheet and then transfer to racks to cool.
*At this point I use a small ice cream scoop to form balls, put them close together on a pan small enough to put into the freezer, then freeze at least one hour. You may then put the cookies in freezer bags and take out as many as you want to bake at a time. They should be thawed slightly on the baking sheet before putting them in the oven.