Prepare the spaetzle according to package directions, or use store-bought spaetzle.
Cut 3 onions into cubes. Sauté them in a saucepan over medium heat for 5-7 minutes until translucent. Add the sweet cream and a pinch of broth or fondor. Stir in the cream cheese. Bring to a simmer and cook for 2 minutes to reduce slightly. Taste and add more broth if needed for stronger flavor.
Grate the Edam cheese.
Grease a 20 cm (8 inch) diameter, 7 cm (3 inch) deep baking dish with butter. Layer the spaetzle, grated cheese, and sauce in the dish 3 times, finishing with sauce on top.
Cut the remaining onion into rings. In one pan over medium heat, cook the onion rings for 3-5 minutes until lightly browned. In another small pan, melt butter over medium heat, add the breadcrumbs, and cook for 2-3 minutes until lightly browned.
Spread the browned onion rings on top of the spaetzle in the baking dish. Top with the browned breadcrumbs. Place the baking dish in a preheated 200 °C (392 °F) oven and bake for 20 minutes until heated through.