Butternut Bisque with French Onion Toast Topper

Ingredients

• 3
  tablespoons butter
• 1
  ½ cups chopped onion
• 1
  ½ teaspoons kosher salt
• 2
  tablespoons tomato paste
• 1
  (2 pound) butternut squash - peeled, seeded, and cut into 1-inch cubes
• 4
  cups low-sodium chicken broth
• 1
  pinch cayenne pepper
• ½
  cup heavy cream
• 2
  tablespoons pure maple syrup
• 1
  tablespoon chopped fresh parsley, or to taste
• 3
  tablespoons butter
• 1
  tablespoon olive oil
• 3
  large sweet onions, chopped
• 1
  large shallot, thinly sliced
• ½
  teaspoon salt
• ¼
  teaspoon ground black pepper
• 2
  tablespoons sherry
• ½
  cup low-sodium beef broth
• 2
  each fresh thyme sprigs
• 6
  slices sourdough bread
• 6
  teaspoons butter, softened
• 6
  ounces shredded Gruyere cheese