Line the bottom and sides of a greased 15x10x1 inch baking pan with parchment paper. Grease the paper and set aside. In a small mixing bowl, beat cream cheese and milk until smooth. Add flour and salt, mix until combined. In a large mixing bowl, beat the eggs until blended. Add cream cheese mixture; mix well. Pour into prepared pan.
Bake at 375 degrees for 30-35 minutes or until eggs are puffed and set. Remove from the oven. Immediately spread with mustard and sprinkle with 1 cup cheese.
Sprinkle with ham, onions and 1 cup cheese. Roll up from a short side, peeling parchment paper away while rolling. Sprinkle top of roll with the remaining cheese. Bake 3-4 minutes longer or until cheese is melted.