Heat olive oil in a large nonstick skillet or Dutch oven over medium-high heat. Add shallot; cook, stirring, until fragrant, about 30 seconds. Add spinach and cook, stirring, until just wilted, about 2 minutes.
Heat margarine in a small saucepan over medium-high heat. Add flour and cook, stirring, until smooth and bubbling, about 30 seconds. Add milk, nutmeg, salt and pepper; cook, whisking constantly, until thickened, about 1 minute. Stir the spinach into the sauce.
Sprinkle with grated cheese and best served hot!