1 1/2 cups whole milk
1 teaspoon vanilla extract
1 cup butter
1 cup packed brown sugar
1/2 cup packed light brown sugar
1/2 cup packed dark brown sugar
1/2 cup white sugar
1 egg, separated
1 tablespoon cornstarch
3 teaspoons baking soda
1 teaspoon salt
1/2 cup chopped pecans
Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
In a heavy saucepan over medium heat, combine milk, vanilla extract, butter, brown sugar and brown sugar. Heat to 350 degrees F (175 degrees C).
Remove from heat, and pour into the greased cookie sheets.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely. Cool completely on wire rack. Refrigerate remaining cookies until ready to use.
To make the frosting: In a medium bowl, mix together brown sugar, white sugar and egg. Beat eggs in small batches until thick. Mix in cornstarch. Pour mixture over the cooled cookies.