Melt 1 tablespoon of unsalted butter in a large pot over medium heat. Add the sliced mushrooms and sauté for 3-4 minutes without stirring to allow them to brown nicely. Afterward, flip the mushrooms and cook for another 3-4 minutes until both sides are caramelized and golden. Once done, remove them from the pot and set aside for later.

In the same pot, melt the remaining butter over medium heat. Add the diced onions, chopped celery, shredded carrots, and minced garlic. Sauté the mixture for 4-5 minutes, stirring occasionally, until the onions become translucent and the vegetables are softened.

Sprinkle the all-purpose flour over the softened vegetable mix and stir well to combine. Cook for about 1-2 minutes, allowing the flour to absorb the flavors and create a roux.

Gradually pour in the half-and-half and low-sodium chicken broth while continuously stirring to prevent lumps from forming. Bring the mixture to a gentle boil, then reduce the heat to low. Let it simmer for 2-3 minutes, stirring occasionally until the soup thickens slightly.

Once simmering, add the potato gnocchi and fresh spinach (if using) to the pot. Increase the heat to medium-low and cook for about 4-5 minutes, or until the gnocchi are tender and float to the surface.

Finally, gently stir the sautéed mushrooms back into the soup and cook for an additional 4-5 minutes. Make sure everything is heated through before removing the pot from the heat.

Ladle the creamy mushroom gnocchi soup into bowls and garnish with freshly chopped parsley. Serve immediately, ideally with crusty bread on the side for dipping.