1 cup butter
1¼ cups dark brown sugar
½ cup granulated sugar
1 egg yolk
1 teaspoon pure vanilla extract
2 cups flour
1 cup rolled oats (not quick cooking)
½ teaspoon baking soda
½ teaspoon salt
¼ teaspoon ground cinnamon
1 cup white chocolate chips
1 cup chocolate chips (I use half milk, half semisweet)
In a medium saucepan, melt the butter over medium heat until melted. Remove from the heat.
Add the dark brown sugar and granulated sugar and stir until smooth. Chill the mixture for 10 minutes.
Remove from the refrigerator and stir in the egg, egg yolk, and vanilla.
Add the flour, oats, baking soda, salt, and cinnamon and mix together.
Stir in the white chocolate chips and chocolate chips.
Roll by hand into 24 medium-size balls or use a scoop, and place on a light-colored cookie sheet. (I wanted a little bit smaller cookie but still did generous scoops and got closer to 40 cookies).
Chill for 30 minutes.
Preheat the oven to 325 degrees F. Remove the cookies from the refrigerator and bake for 12 to 14 minutes.