Creamy Spinach and Mushroom Tortellini with Caramelized Onions

Peel the onions, wash them and thinly slice them.
Heat 2 tablespoons olive oil on medium-high heat in a large skillet. Add sliced onions and cook on high heat for about 10 minutes, constantly stirring with the spatula.
Reduce heat to medium and continue cooking the onions for 10 more minutes, continuing to stir, as onions brown even more without burning. At this point add a pinch of salt over the onions.
Continue cooking for 10 more minutes on medium or low heat, stirring occasionally to make sure onions don’t stick to the bottom of the pan or burn.
In total, you should have cooked onions for 30 minutes. Remove the onions from the skillet onto a plate.

Heat 1 tablespoon olive oil in the same skillet on medium heat. Add sliced mushrooms. Sprinkle with a pinch of salt. Cook mushrooms for about 5 minutes, occasionally stirring, until mushrooms are soft.
Add fresh spinach to the skillet and stir on low heat just until spinach starts to wilt.
Add back the caramelized onions.
Add 1 cup of heavy cream and ¼ teaspoon salt to the mushroom and spinach mixture and bring to a quick boil. Immediately reduce to simmer. Keep stirring while the sauce simmers for a couple of minutes.

Cook tortellini according to package instructions. Usually, that means to bring a large pot of water to boil. Add tortellini and boil for 7 to 10 minutes. Drain.
Add cooked and drained tortellini to the creamy sauce. Stir on low heat for a couple of minutes to reheat.
Top with cracked black pepper when serving.

Helpful Tips about Caramelized Onions.

Make-ahead tip. Make caramelized onions ahead of time, refrigerate them in an air-tight container, and use within the next 3 days.
You can also freeze caramelized onions for up to 2 months and thaw them whenever you need them.

Substitutions for heavy cream

Half-and-half. You can use 1 cup of half-and-half instead of heavy cream. Bring half-and-half to boil, then add 1/s cup of shredded Parmesan cheese. Reduce to simmer. Keep stirring while the sauce simmers until the cheese melts.
Coconut milk. Use 1 cup of coconut milk to replace 1 cup of heavy cream. Follow the recipe as is.

Other Substitutions

Use button mushrooms, portobello, cremini, shiitake or oyster mushrooms.
Good substitutes for spinach are kale and arugula.
You can also use pre-made ravioli, gnocchi or short pasta (such as bow-tie or penne pasta) instead of tortellini.
Substitute tortellini with gluten-free ravioli or gluten-free short pasta, such as gluten-free bow tie pasta. You can also use gluten-free gnocchi (be sure to check the packaging as not all gnocchi is gluten-free).
Protein. You can add grilled steak, pork chops, or chicken. You can also serve this with fish, shrimp, or scallops.