Slice and dice the onions and garlic, set aside.
Season the chicken breasts with salt and pepper on both sides.
Sear the chicken in a skillet with a little olive oil until golden brown on both sides.
Remove the chicken from the skillet and add the onions and garlic. Cook for a few minutes until fragrant.
Deglaze the skillet with a bit of the chicken stock, scraping up any browned bits.
In a bowl, whisk together the remaining chicken stock, heavy cream, and chicken gravy mix.
Add the seared chicken, onion-garlic mixture, and sun-dried tomatoes to a crockpot.
Pour the cream sauce over the top.
Cover and cook on high for 4 hours or low for 8 hours, until the chicken is very tender.
Shred the chicken in the crockpot using tongs.
Add the fresh spinach, cover, and cook for 5 more minutes until the spinach is wilted.
Serve the chicken and sauce over cooked tortellini, noodles, rice, or mashed potatoes.
