Apple Crisp Cookie Pizza

1 pouch Betty Crocker™ oatmeal cookie mix

1/2 cup butter, softened

1 egg

1 tablespoon water

1/3 cup old-fashioned oats

1/3 cup pecans or walnuts, chopped

1/4 cup butter, cold and cut into cubes

3 medium apples, cored and thinly sliced

1 teaspoon lemon juice

1/3 cup granulated sugar

1/2 teaspoon ground cinnamon

1 cup powdered sugar, sifted

2 to 3 tablespoons milk

1 teaspoon vanilla