Heat the olive oil in a large nonstick skillet over medium heat. When the oil is hot and shimmering, add the gnocchi in an even layer. (I like to smack the bag on the countertop several times before opening it to help break up any gnocchi that have stuck together.) Let the gnocchi cook undisturbed until they’re golden brown on the undersides, about 3 minutes. Flip the gnocchi with a spatula and continue to cook until browned and crisped all over, another 5 to 8 minutes. (The gnocchi will release itself from the pan when it’s ready to be flipped for the first time! Don’t rush the initial sear or they’ll stick to the pan and break apart.) Transfer the gnocchi to a bowl or plate and briefly set aside.
Pre-heat the broiler on high.
Add the sausage to the skillet and cook for about 5 minutes, stirring and breaking up the meat into small pieces with a spatula, until browned. Reduce the heat to low and stir in the tomato sauce. Add the spinach to the pan and cook for about a minute, just until wilted. Return the gnocchi to the pan, folding it into the sauce. Sprinkle the cheese over the contents of the the skillet.
Transfer the skillet to the broiler. Broil for about 2 minutes or until the cheese is melted and bubbling. (Keep a close eye on it! Broilers are fickle.)
Divide the skillet between two plates or bowls and serve warm. Garnish with basil and crushed red pepper if you like.