Choose baby leaves, 4 to 6 inches in length, for the mildest taste and most tender greens. Mature leaves have a much more pungent flavor and are best boiled until tender. This simple sauté takes just a few minutes to cook and makes a lovely accompaniment to roast chicken or steak.
Heat the oil and butter in a large skillet or Dutch oven over low heat, and add the garlic. Cook gently, stirring frequently, until the garlic is fragrant but does not take on any color.
Add the moist greens, raise the heat to medium-high, and cover the pan. Cook until the greens wilt, about 2 minutes, shaking the pan once or twice. Remove the cover; if there's any excess liquid, cook until it evaporates.
Toss the greens with the lemon juice, salt, and pepper, and serve hot.