Chocoholic Cookies

Chocoholic Cookies
2 cups rolled oats
2 cups (1 12-ounce package) semisweet chocolate chips
1 cup (2 sticks) unsalted butter, softened to room temperature
1 cup firmly packed dark brown sugar
1/2 cup granulated sugar
1 1/2 cups all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon salt
1/4 cup unsweetened cocoa
1 tablespoon milk
1 1/2 teaspoons pure vanilla extract
2 large eggs, slightly beaten
2 cups (1 12-ounce package) white chocolate chips

Preheat oven to 350 degrees F. Spray 2 cookie sheets with cooking spray. Do not alter the order in which the ingredients are combined. In a large bowl, combine the oats and chocolate chips, set aside. In another large bowl, beat together the butter and sugars until creamy. Sift together the flour, baking soda, salt, and cocoa, and then add to the butter mixture, stirring until thoroughly combined. The batter will be very stiff. Stir the milk and vanilla into the eggs, and then stir this mixture into the butter mixture until thoroughly combined. Add the chips and oats, stir until well mixed. Using a two-tablespoon scoop, drop batter 2 inches apart on cookie sheets. Bake 9 to 12 minutes, until cooked through.
Cool on pan 4 minutes, transfer to wire racks to cool completely.
Melt the white chocolate in the top of a double boiler over simmering water. Frost the cooled cookie with the melted white chocolate. Refrigerate for 10-15 minutes until all the chocolate cools and sets. Store between layers of wax paper in an airtight container in a cool place.
(from The Main Corpse, Diane Mott Davidson mystery)