Wash the greens, but do not dry. Trim the large stems and coarsely chop. Set aside.
Warm 3 tablespoons of olive oil in a large, heavy pot over medium-high heat. Add the onions and saute for 4 minutes. Add the garlic and saute for 4 minutes longer. Add the greens, chicken broth, soy sauce, and pepper. Cook, stirring often, until the greens have wilted and become tender, about 7 to 10 minutes.
Transfer the cooked greens to a serving plate and crumble the ricotta salata cheese over the top.