Using older (or more fermented kimchi) kimchi is perfect for this recipe. I buy my kimchi at Hmart (korean grocery store) and I love the Jongga brand in the foil packaging or plastic tubs! I also think Mother in Law's (sold at whole foods!) kimchi is super fermented and would work for this recipe. If you want to use up more of your old kimchi, make this Dubu Kimchi (Tofu with stir fried kimchi and Pork).