Melt the Spiced Butter in a large stockpot over medium-high heat. Add the onion and chiles and saute until the onion has softened, about 5 minutes. Add the collards and stir in the vinegar, brown sugar, and salt to taste and bring to a simmer. Turn the heat down to low, cover, and simmer until the greens are very tender, about 1 1/2 hours. Serve hot or warm.
Melt the butter in a saucepan over low heat. Add the garlic, shallots, ginger, coriander, cumin, fenugreek, ajwain, black pepper, cinnamon, and turmeric. Simmer very gently for 30 minutes to infuse the flavors. Keep an eye on this; you don't want the milk solids to brown.
Skim off all the foam and any floating seeds and let the butter sit for about 10 minutes for the milk solids to settle on the bottom.
Carefully pour the spiced butter through a sieve lined with a few layers of cheesecloth into a container, leaving the solids behind. Let it cool, then cover and refrigerate. It will keep for months. Yield: 3 cups