Pan-Crisp the Gnocchi: Heat 1 tablespoon olive oil and 1 tablespoon butter in a large 12-inch heavy cast-iron skillet over medium-high heat. Add the uncooked potato gnocchi straight from the package in a single layer. Sear without moving for 3 to 4 minutes until golden and crisp on the bottom. Toss and cook for another 2 to 3 minutes until pillowy inside with a crispy crust. Transfer to a clean plate.

Caramelize the Mushrooms: In the same hot skillet, add remaining 1 tablespoon olive oil and 1 tablespoon butter. Add the sliced cremini mushrooms in an even layer. Let them brown undisturbed for 3 to 4 minutes to release moisture and develop deep caramelization. Season with sea salt and cracked black pepper, then sauté for 2 more minutes until tender and deeply golden.

Aromatize & Deglaze: Reduce heat to medium. Add the minced garlic and fresh thyme leaves to the skillet with the mushrooms. Sauté for 60 seconds until fragrant, taking care not to scorch the garlic. Pour in the vegetable broth and fresh lemon juice to deglaze the pan, scraping up all the savory browned bits stuck to the bottom.

Simmer the Sauce: Pour in the heavy cream and a pinch of ground nutmeg. Bring to a gentle simmer for 2 to 3 minutes over medium-low heat until the sauce begins to reduce and coat the back of a spoon.

Fold in Cheese & Gnocchi: Lower heat to low. Stir in the freshly grated Parmigiano-Reggiano cheese until completely melted and silky smooth. Return the crispy pan-seared gnocchi (and baby spinach if using) back into the skillet. Gently toss to coat every pillowy gnocchi dumpling in the velvety garlic cream sauce for 1 to 2 minutes.

Garnish & Serve: Remove from heat. Garnish generously with additional shaved parmesan, fresh thyme sprigs, and cracked black pepper. Serve warm straight from the skillet or in shallow ceramic bowls with crusty bread.