Cornstarch is the secret behind a creamy and smooth cheese sauce made without using wheat flour. This sauce formula can also be adapted using any number of cheeses, and can be used anywhere you like to have a cheese sauce (e.g. baked potatoes, cooked broccoli, etc.).
For the sauce whisk the milk, cornstarch and mustard together in a medium saucepot and then bring it up to a full simmer over medium heat, whisking constantly until it has thickened and is glossy. Reduce the heat to medium low and whisk in the cheese in 2 additions, whisking until smooth after each addition. Season to taste and keep the sauce warm until ready to assemble.
In a large sauté pan, add the oil, onion and peppers over medium-high heat, sautéing until soft, about 3 minutes. Add the spinach and wilt, then stir in the red pepper, garlic, basil and olives to warm. Season to taste.
Place the cooked, warm rice pasta in a baking dish and spoon the vegetables over. Pour the warm cheese sauce onto the pasta and stir well to coat. Top with grated Parmesan and bake at 375ºF for about 20 minutes until the sauce is bubbling at the edges. Serve immediately.