Tear kale into large pieces, then cook in a large pot of well-salted boiling water, uncovered, until tender, about 6-10 minutes. Drain kale, and, when cool enough to handle, press out excess liquid.
Cook walnuts in oil in a 12-inch heavy skillet over medium-low heat,stirring occasionally, until pale golden, about 5 minutes. Stir in garlic and cook, stirring, until very fragrant, about 1 minute. Add kale and salt and pepper to taste and cook, tossing, until heated through.