Cook gnocchi according to package directions, reserving 1 cup of cooking liquid.
Place a large nonstick skillet over medium heat and add the walnuts. Toast, shaking the pan frequently, about 3 to 4 minutes. Transfer the toasted walnuts to a plate.
Return the skillet to medium-high heat with 1 tbsp olive oil. Once hot, add the sliced mushrooms and a pinch of salt and cook until browned in places, about 4 to 5 minutes. Add the minced garlic, minced shallot, and a pinch of salt and pepper and cook until softened, about 3 to 4 minutes.
Add the butter to the skillet with the mushrooms, increase the heat to high, and add the cooked gnocchi. Cook, stirring occasionally until browned in places, about 3 to 5 minutes.
Add the sherry wine to the skillet with the gnocchi and cook for 1 minute. Add the reserved pasta water and broth concentrate. Stir well, bring to a boil, and cook until slightly thickened, about 2 to 3 minutes. Add the baby spinach to the skillet and cook until wilted, about 2 to 3 minutes.
Serve topped with walnuts.