1. Fill the sink with clean water. Remove the stems from all of the greens and wash both the leaves and the stems three times, refreshing the water each time. Drain thoroughly and use a kitchen towelt to help remove the excess water from the greens.

2. Prepare the stems by slicing them once lengthwise, then finely chopping the cut stems crosswise; set aside. In a large saucepan set over medium heat, warm the canola oil. Add the onions and garlic; using a wooden spoon, stir constantly until translucent, about 5 to 7 minutes. Add the chile flakes and stir until fragrant, about 30 seconds.

3. Stir in the chopped stems and cook until slightly tender, about 6 minutes. Season with sea salt and pepper then add the leaves of the greens in three batches, letting each batch wilt slightly to make room for next batch. Once all of the greens are in the pot, season lightly with sea salt and cracked pepper.

4. Add the cider vinegar and cover the saucepan. Reduce the heat to low and simmer, stirring occasionally, until the greens are tender and broken down, about 30 to 40 minutes.

5. Remove the pot from the heat and set aside to cool. Remove the cooled greens from the pot and chop finely. Return the greens to the braising liquid (they can be covered and refrigerated for up to two days). When you're ready to serve the greens, bring them and their liquid to a simmer. Add the butter and stir until melted. Season with salt and pepper and serve.