Bring a large pot of salted water to a rolling boil over high heat. Add the spaghetti and cook according to package instructions, typically about 8-10 minutes, until al dente. Stir occasionally to prevent sticking. Once done, drain the spaghetti, but be sure to reserve about a cup of the starchy pasta water for later use.

While the pasta cooks, wash and chop fresh spinach if using, or thaw and press excess moisture from frozen spinach. In a large skillet, add a splash of olive oil and heat over medium heat. Once the oil shimmers, add the spinach and sauté for 2-3 minutes until it wilts down, turning beautifully bright green.

To the wilted spinach in the skillet, add minced garlic, if using, and cook for about 30 seconds until fragrant but not browned. Next, lower the heat and stir in the cream cheese, letting it melt into the spinach. Gradually pour in the cream while stirring, creating a velvety, creamy sauce that coats the spinach evenly.

As the sauce thickens, season it with salt, pepper, and a pinch of nutmeg to enhance the flavors of your 15-minute spaghetti with spinach and cream cheese sauce. Taste the sauce and adjust the seasoning if necessary, allowing it to simmer gently for another minute to meld the flavors beautifully.

Add the drained spaghetti directly into the skillet with the creamy sauce. Toss everything together, adding reserved pasta water, a little at a time, to achieve your desired creamy consistency. Stir until the spaghetti is well-coated and heated through, ensuring each strand is enveloped in that luscious sauce.

Once the spaghetti is beautifully coated with the cream cheese sauce, remove it from the heat. Plate the dish and garnish with halved cherry tomatoes and freshly chopped herbs of your choice, adding vibrant color and freshness. Serve immediately for the best experience of your delicious 15-minute spaghetti with spinach and cream cheese sauce.