Heat the plant-based butter, ghee, or olive oil in a large pot over medium heat. When using an Instant Pot, select the Sauté setting.
Add the finely diced yellow onion and cook for approximately 5 minutes, or until it begins to soften.
Stir in the minced garlic and continue cooking for another 2 minutes, just until fragrant.
Add the garlic salt, dried oregano, thyme, paprika, and crushed red pepper flakes to the softened onion and garlic, stirring to distribute the seasonings evenly.
Arrange the chicken breasts or thighs in the pot. Pour in 4 cups of chicken broth, then incorporate the tomato paste, petite diced tomatoes, chopped sun-dried tomatoes, and nutritional yeast.
For the stovetop method, bring the soup to a boil. Reduce the heat to maintain a medium simmer, cover the pot, and cook for 10–15 minutes, stirring occasionally to prevent ingredients from catching on the bottom. Continue until the chicken is fully cooked.
For the Instant Pot method, secure the lid and cook using the Soup or Manual setting for 10 minutes.
While the chicken cooks, steam the cauliflower rice according to the directions on its package.
Transfer the cooked cauliflower rice to a blender. Add the remaining 1 cup of chicken broth along with the vegan heavy cream or unsweetened coconut cream.
Blend on high speed until completely smooth and velvety.
Once fully cooked, remove the chicken from the soup and shred it with two forks or a mixer.
Place the shredded chicken back into the pot, then pour in the blended cauliflower cream mixture and stir until thoroughly incorporated.
Add the chopped spinach and allow the soup to simmer for approximately 5 minutes, or until the spinach has wilted.
Taste the soup and season with additional garlic salt if required.
Divide the hot Marry Me Chicken Soup among serving bowls.
Finish each portion with freshly chopped basil and, if desired, an additional light seasoning of garlic salt.