Preheat the oven to 380F. Put a pan over medium high heat and add oil, fry the ground meat with onions for 10 minutes, stirring occasionally. At the end, add salt and pepper, mix.
While the meat is cooking, mix the ingredients for the sauce - sour cream, mayonnaise, mustard, Worcester. sauce, spices, sugar.
Add half of the grated cheddar to the skillet. Stir and let the cheese melt (1-2 minutes). Transfer the meat mixture to a 9x9 or 8x8 baking dish. Whisk together two eggs and heavy cream, pour on top.
Put the remaining cheese on top. Put the baking dish in the oven and bake for 25 minutes. Let the casserole cool slightly, then spread it with big mac sauce.
Sprinkle the lettuce on top, and then lay out the pickle slices. Cut into pieces and serve.