Skillet Chicken Pot Pie with Butternut Squash

INGREDIENTS

• Kosher salt, freshly ground pepper
• 3 cups low-sodium chicken broth
• 1 tablespoon chopped fresh sage
• 1/4 cup all-purpose flour
• 1/2 small butternut squash, peeled, cut into 1/2" pieces (about 1 1/2 cups)
• 1 large egg
• 1 sheet frozen puff pastry (such as Dufour or Pepperidge Farm), thawed
• 4 garlic cloves, finely chopped
• 1 small bunch kale, center ribs and stems removed, leaves chopped
• 1 cup frozen white pearl onions, thawed
• 1/4 cup olive oil
• 1/2 rotisserie chicken, meat torn into bite-size pieces (about 1 1/2 cups)