Preheat oven to 350 degrees F. Beat egg yolks together with salt. As they start to thicken, add the sugar substitute, cheeses, and sour cream. Beat until light and fluffy. Add 1/2 teaspoon lemon juice, vanilla, and pudding.
Beat the egg whites. Fold half of the beaten egg whites into the cheese mixture, and then tranfer this back into the beaten egg whites. Fold gently until incorporated.
Mix the soy milk with the coffee. If desired, add 1 teaspoon cocoa powder to the coffee mixture. With a wooden spoon or spatula, mix the coffee and the cheese mixture.
Pour the batter into an 8-inch greased pie pan. Place this pan into a larger pan filled with 1 inch of water. Bake for 40-50 minutes. (The center should be neat and firm when lightly shaken). Remove from the water and bake for an additional 10 minutes.
Whisk together the topping ingredients. Spoon over hot pie, spreading to the edges with a metal spatula (or the back of a spoon) dipped in water. Bake at 375 degrees F for 5 minutes. Turn off the heat and leave in the oven for an additional 30 minutes.