Bring water and salt to a boil in a large stockpot. Add greens and boil, uncovered, for 7-8 minutes. Drain greens in a colander, pressing on them with the back of a spoon to squeeze out excess water.
In a 12-inch non-stick skillet, heat olive oil and add olives, sautéing for 60 seconds. Add garlic and sauté for another 30-60 seconds, until the garlic softens but does not turn brown. Add the drained greens and stir well to combine, grinding a bit of black pepper into the pan. Cook, uncovered, for another 3-4 minutes, stirring occasionally, to evaporate water and combine flavors.
Turn off heat, sprinkle feta on top and put lid on pan. Let pan set on stove for a minute or more, to soften cheese. (Dish should not need additional salt because of salty olives and salty cheese.)
Note: If you have black oil-cured olives, try those in this dish. And feel free to substitute flavored feta if you like.
Recipe by Dorothy Reinhold, Shockingly Delicious