• Preheat the oven to 375˚F.
• Spray or butter a 9x13 casserole dish.
• Place carrots, celery, potatoes, and chicken cubes in a medium saucepan and cover with water (~4 cups). Bring to a boil for 1 minute, and then cover and simmer on medium heat until vegetables are soft (~10-15 minutes).

  Pro tip: It will foam a bit for the first few minutes, but that is normal.
  3 cups carrots, 1 cup celery, 2 cups peeled and cubed potatoes, 1 lb chicken breast
• Drain the vegetables and chicken, add the peas, and set them aside.
  3/4 cup frozen peas
• While the vegetables are cooking, heat a large frying pan over medium-low heat.
• Melt butter and cook onion over medium-low heat until softened (~5 minutes).
  1/3 cup salted butter, 1/3 cup white onion
• Add garlic, salt, pepper, celery seed, and parsley. Cook for 2 minutes, stirring often.
  4 cloves garlic, 1 tsp sea salt, 1/2 tsp black pepper, 1/4 tsp celery seed, 1 tsp dried parsley
• Sprinkle butter mixture with flour, whisking slowly. Cook for 3 minutes, stirring often.
  1/4 cup all-purpose flour
• Slowly whisk in chicken stock, warmed whole milk, whisking constantly to incorporate.
  1 1/2 cup chicken stock, 1 1/4 cup whole milk
• Increase the temperature to medium heat and whisk slowly while it cooks down for 5 minutes.
• Combine cooked vegetables and chicken in the buttered 9x13 dish.
• Pour or spoon the warm sauce over the top of the vegetables and chicken. Gently stir to combine.

Make the Biscuit Topping

• Mix all the dry ingredients in a medium bowl. 
  2 cups all-purpose flour, 1/2 tsp salt, 1/2 tsp baking soda, 1 tsp baking powder, 1 tsp dried parsley, 1 tsp dried rosemary, 1/4 tsp onion powder, 2 tsp garlic powder, 1/2 tsp dried sage
• Add the melted butter, mix, and then add milk, and mix everything until just combined.
  5 tbsp salted butter, 1 1/3 cups whole milk

Assemble the Casserole

• Drop spoonfuls of the biscuit topping over the top of the chicken and veggie mixture.
• Bake uncovered for 30-37 minutes or until the biscuit topping is lightly browned.
If the biscuits are browning too quickly but the casserole isn't done cooking, you can loosely tent the top of the baking dish with foil.
• Remove from the oven and let stand for 10-15 minutes before cutting/serving.