Preheat oven to 350 degrees. Grease a 9-inch square or 7-by-11 inch baking pan.

Chocolate Layer

1. In heavy saucepan over medium heat, combine the butter, chocolate chips, milk and sugar. Cook, stirring, until melted and mixed together.
2. Remove from heat and stir in nuts. Set aside to cool while you make the cookie layer.

Cookie Layer

1. With an electric mixer using the whisk attachment, cream together the butter and sugar. Add the egg and vanilla and continue beating until light and fluffy.
2. In a separate mixing bowl, stir together the flour, baking soda and 1 3/4 cups of the oats. Beat into the butter mixture just until blended.
3. Press 3/4 of the cookie dough into the bottom of the prepared pan, pushing down with moistened fingers into a tight, even layer.
4. Spread the cooled chocolate mixture evenly over the top.
5. Mix the remaining 1/4 cup oats into the remainder of the cookie dough. Sprinkle evenly over the chocolate layer.
6. Bake for 25 to 30 minutes.
7. Cool in pan on a wire rack to room temperature, then cover and refrigerate before cutting into 36 bars. (I cut them into 18 pieces, then cut those in half.) Store in the refrigerator in an airtight container.