1 1/2 pounds butternut squash, peeled and seeds removed
2 tablespoons butter or olive oil
1 cup uncooked pearl barley
1 leek, white and light green parts only, thinly sliced
1/4 cup white wine
4 cups low-sodium chicken or vegetable stock (preferably homemade)
1 teaspoon fresh thyme leaves, minced
1/4 teaspoon salt, or more to taste
2 teaspoons fresh lemon juice
1/4 cup toasted pecans, chopped
Grated Parmesan cheese (optional)