To Roast The Pine Nuts : place the pine nuts in a small skillet over medium heat. I have a nine inch cast iron skillet that works great for small jobs like this. Cook the pine nuts, stirring them as they cook until they are a golden brown color. Remove the pine nuts from the pan to a small bowl.
Place the butter in a 12 inch skillet over medium heat. After the butter melts, continue cooking it until it starts to foam a little and turns a golden brown color. Watch carefully, the butter can turn from a beautiful golden brown too burnt in a second. Remove the browned butter and the browned bits on the bottom of the pan (the browned bits are flavor) to a small bowl and set it aside. Start cooking the gnocchi according to the package directions. Pour half of the browned butter from the bowl into the 12 inch pan that you melted it in. The browned butter bits will be at the bottom of the bowl, we're not going to use them at the moment, keep the browned butter bits at the bottom of the bowl while you pour half the browned butter into the skillet.Add the garlic and mushrooms to the browned butter you poured into the skillet. Cook the mixture until the mushrooms are golden brown. Stir the salt and pepper into the mushrooms, reduce the heat too low on the stove burner and stir in the spinach. Cook the spinach until it's wilted. Place the drained cooked gnocchi in the pan. Add the remaining browned butter (with the browned butter bits) to the pan along with the lemon juice. Stir the mixture together and add the toasted pine nuts. Serve immediately.