Preheat oven to 350°F with rack in centre position.In a blender, combine eggs, milk, salt and pepper (you can whisk in a bowl if you prefer but blending will give you a fluffier frittata). Add parsley and slowly blend just to combine. Set aside.Warm olive oil in a medium (10-inch) ovenproof skillet, preferably cast iron, over medium-high heat.Add pancetta and cook until crispy, about 5 minutes.Add kale and red pepper and cook until kale wilts, about 2 minutes.Distribute pancetta and vegetables evenly over the base of the skillet and then pour in egg mixture and sprinkle with chives.Cook for a minute or two until the egg at the edges of the skillet begin to set.Transfer to oven and bake until set in the middle and the top is golden, about 25 minutes.If you prefer a crispy top, run the frittata under the broiler for a minute or two at the end of cooking.Remove from oven and let stand for 5 minutes. Cut and serve.