Preheat the oven to 375°F.
Season the chicken with salt and pepper.
Heat a nonstick pan on medium heat. Once hot, add in the oil. Sauté the chicken and onion until the chicken has a nice golden brown on all sides. Add in the spinach and sauté until wilted. Then remove the contents from the pan to cool down for about 5 minutes.
Combine the eggs, cream, cheese, tarragon, and season with salt and pepper in a bowl. Stir in the chicken, spinach, and onion.
Pour the mixture into the pie crust.
Bake until a toothpick inserted into the center comes out clean (about 25 to 30 minutes). Remove from the heat, and let stand for 5 minutes before cutting into wedges and serving warm.
Serve with crackers, garnish with tarragon