Chicken Pot Pie with Flaky Biscuit Topping

Bahan-bahan (12 porsi)

• 1/2 cup butter ((1 stick))
• 1/4 cup olive oil
• 1 large onion (chopped)
• 4 large carrots (chopped)
• 1 & 1/2 cups celery (chopped)
• 3/4 cup flour
• 3 cups chicken broth
• 1 & 1/2 cups milk
• 1 & 1/2 teaspoons kosher salt
• 1 teaspoon pepper
• 1/2 teaspoon celery seed
• 1 pound rotisserie chicken (shredded)
• 1 & 1/2 cups frozen peas
• buttermilk or milk (for brushing)