In a large, wide bowl, whisk together the eggs, egg whites, buttermilk, honey, vanilla, cinnamon, ginger, nutmeg, and salt.
Over medium heat, heat a heavy nonstick skillet, or a pair of skillets, large enough to hold all the French toast slices in a single layer without crowding. Dip the bread slices into the egg mixture, turning them and making sure they are completely saturated.
Spray the heated skillet or skillets with nonstick cooking spray. Add the soaked bread pieces and cook until golden brown on both sides, 5 to 7 minutes total.
To make the fresh berry compote, in a non-reactive saucepan, combine the blueberries, raspberries, honey, orange zest, orange juice, and salt. Bring to a simmer over medium heat, stirring occasionally, and continue simmering just until the berries have given up some of their juices and have turned slightly syrupy, 3 to 4 mins. Transfer to a serving bowl and keep warm.
Arrange 2 slices of the French toast on each of four heated serving plates. Spoon some of the compote over each serving. If you like, spoon a little confectioners’ sugar into a small, fine-mesh sieve held over each plate and tap the sieve lightly to dust the French toast. Garnish with fresh berries and serve with more berry compote on the side.