Preheat the oven to 350 degrees Fahrenheit. In a small skillet or saute pan, warm the olive oil over medium-low heat. Add the onion and garlic, and cook, stirring frequently, for 4-5 minutes or until the onion is somewhat translucent. Toss together the artichoke hearts, spinach, onion and garlic mixture from the skillet (including oil), black pepper, and chili flakes (if using), and divide equally among whatever vessels you plan to cook the dip in (I used two of the 1-cup ramekins that you see pictured & one glass Pyrex dish of a similar size). Keep in mind that the spinach will shrink significantly once the hot cashew cheese hits it.