For the spinach, heat a medium size skillet over medium heat with the oil, two turns of the pan. Add the onion or shallots and garlic and soften, 5-7 minutes. Melt in the cream cheese, then add the cream or half-and-half to thin a bit and season with nutmeg, salt and pepper. Add the spinach and heat through; add grated cheese.
For the burgers, combine the sirloin with Kosher salt, Worcestershire sauce and pepper and form four large patties that are thinner at center and thicker at the edges for even cooking. Heat a cast iron skillet over medium heat and add the burgers. Add the consommé or stock to the pan to deglaze.
Place the burgers on the buttered toast: set the burgers on top, drizzle with stock and top with creamed spinach and crispy onions.