For the apple topping: In a bowl, toss the sliced apples with the lemon juice and set aside.
In a large saucepan, melt the butter. Add the apples, salt, and both sugars. Mix well to combine. Cook, stirring occasionally, until the apples are soft and have begun to release some of their juices, about 8 to 10 minutes.
Add in the cinnamon and cornstarch. Mix and allow mixture to thicken, about 2 minutes. Remove from heat.
For the French toast: In a shallow bowl, whisk the eggs and milk together. Dip both sides of croissants in egg mixture. Melt the butter on a griddle, the cook brown croissants on both sides until golden. Serve French toast topped with the apple topping and whipped cream. Makes 4 servings.