If you don't have crusty bread and need to dry it out: Preheat the oven to 400°F and line a large baking sheet with foil or a silpat mat. Add the cubed sourdough to the baking sheet then drizzle with olive oil or avocado oil then toss gently. Place in the oven for 20 minutes, stirring halfway through, until the bread crisps and turns golden, but doesn’t brown.
To make the stuffing: Preheat the oven to 350°F and spray a 9x13 inch baking pan with cooking spray.
Add 3 tablespoons of grass-fed butter (or vegan butter) to a large saute pan or skillet and melt over medium heat. Add the onion, celery and apple and cook, stirring frequently, until softened and translucent, 2-3 minutes. Add the minced garlic and cook for another minute until fragrant. Add the salt, pepper and all of the herbs and stir well. Remove from the heat and set aside.
In a large bowl, whisk together the eggs then add the prepared celery, onion and apple filling. Add the crusty bread cubes and toss everything to coat. Add the chicken stock and stir again.
Pour the stuffing mixture into the prepared pan and spread it out evenly. Cut the remaining 3 tablespoons of butter (or vegan butter) into chunks and place them on top of the stuffing. Cove
Cover the stuffing with foil and bake in the preheated oven for 25 minutes. Remove the foil from the top and cook for another 8-12 minutes, until it's golden brown.