Total time: 50 minutes
3 tablespoons olive oil
4 cloves garlic, sliced
5 cups trimmed, shredded mustard greens, washed and lightly drained
3 egg yolks
5 egg whites
1/8teaspoon cream of tartar
1. Heat the oven to 375 degrees and generously butter 6 (one-half cup) straight-sided ramekins or individual soufflé molds. Warm the olive oil in a skillet and add the garlic. Cook until the garlic turns translucent, about 3 minutes, then add the mustard greens and cook, stirring, until they are quite soft, about 5 minutes. Cool slightly.
2. Combine the greens mixture, the ricotta, egg yolks and salt in a food processor and purée until smooth.
3. Beat the egg whites until frothy. Add the cream of tartar and continue beating until well-defined, stiff peaks form and retain their shape. Do not over-beat.
4. Gently fold about one-half cup of the greens purée into the egg whites, using a hand-held balloon whisk or a spatula. Cut straight down through the purée and the egg whites, scrape the bottom and lift the egg whites over the purée. Turn the bowl a quarter turn and repeat. Keep doing this until the purée is fully incorporated, 3 or 4 times.
5. Add the remaining purée and fold it in the same way. When you're done, the purée should be evenly distributed but there may be small patches of egg white remaining. Do not over-mix.
6. Using a large soup spoon, divide the soufflé mixture among the ramekins. If you have excess batter, bake it in another ramekin or discard it. (The recipe can be made to this point, covered tightly with plastic wrap and refrigerated for up to 2 hours or frozen for up to a month. Soufflés can be baked straight from the refrigerator. If frozen, remove the plastic wrap immediately and warm at room temperature for 30 minutes before baking.)
7. Put a jellyroll pan in the heated oven and arrange the soufflé ramekins on it. Bake until the tops are puffed and golden brown in spots, 18 to 23 minutes. A sure sign of doneness is when the soufflé becomes extremely fragrant. Do not over-bake, or the center will be dry. Remove and serve immediately.