Brush any soil off mushrooms with a soft brush or clean kitchen towel. Do not wash them. Trim bottoms off stems if they are tough, and slice mushrooms lengthwise. In a large skillet over medium heat, combine oil, garlic, and parsley, and cook until garlic is softened. Add mushrooms and sauté for 2 to 3 minutes. Add chicken stock and continue to sauté until mushrooms are tender, 4 to 5 minutes. Add salt and pepper to taste.

Meanwhile, bring 4 to 5 quarts water to a rapid boil. Add the 1½ tablespoons salt and pasta and stir immediately, continuing to stir frequently to prevent pasta ribbons from sticking together. Drain but don’t overdrain—pasta should be dripping somewhat when combined with sauce. Transfer pasta to skillet with sauce. Toss well and serve. Pass parmigiano at the table, if using.