In a bowl, whisk together the eggs, cream, milk, orange juice, brown sugar, vanilla, orange zest, salt, and Grand Marnier until blended. Soak the bread slices in the egg mixture for 10 seconds per side

Set an electric skillet to medium heat and brush with butter. When the pan is hot cook the bread in batches ( do not overcrowd), turning once until golden and crisp - about 2 min per side.

Transfer the French toast to a baking sheet.
Sprinkle 1 tsp granulated sugar evenly over the surface of each slice.

Using a kitchen torch, move the flame continuously in small circles over the surface until the sugar melts and lightly browns.
Serve immediately with maple syrup and butter.