In a 2- or 4-cup measuring glass or medium bowl, whisk the coconut milk, broth and nutritional yeast. Set aside. (If you have a small whisk, you can measure all the ingredients into a measuring glass and whisk them in that.)
Add the oil to a large skillet and place over medium heat. When the oil is shimmering, add the onion, ½ teaspoon salt and Italian seasoning. Saute, stirring occasionally, until the onions are soft and translucent, about 5-7 minutes.
Add the garlic and red pepper flakes and cook, stirring constantly, until the garlic is fragrant, about 30 seconds.
Add the milk mixture and use the spatula to scrape up the bottom of the pan (adding flavor and making the pan easier to clean later.)
Stir in the sun-dried tomatoes and spinach. Raise the heat to high, bring the sauce to a boil, then reduce the heat to medium-high and let it simmer strongly for 5-8 minutes, until reduced and thickened.
Stir the shrimp into the pan, trying to submerge them as much as possible into the sauce. Let them cook, stirring occasionally, until pink and cooked through, about 5-6 minutes. Add a few grinds of fresh black pepper, then taste and adjust seasonings if necessary. Sprinkle on the fresh herbs, if using, then serve and enjoy!