This simple side salad is delicious paired with roasted chicken and vegetables.
Preheat oven to 350 degrees. Place 1 cup walnuts on rimmed baking sheet and toast in oven 10 minutes. Cool to room temperature and coarsely chop.
Finely chop remaining walnuts and place in small saucepan with olive oil and garlic. Bring to bare simmer over medium heat. Remove from heat, cool to room temperature, and strain oil into medium bowl. Whisk vinegar, salt, and black pepper into oil.
Spread escarole over a large platter. Sprinkle coarsely chopped walnuts and red onion over escarole and drizzle dressing over salad. Shave Pecorino Romano on top and serve immediately.