Crack the eggs into a medium baking dish and whisk lightly. Add the milk, sugar, vanilla and salt and whisk until smooth.
Press down on bread slices to flatten slightly. Soak the bread in the egg mixture until completely soaked through, about 4 to 5 minutes per side.
Heat a square 4 slot waffle maker according to the manufacturer's directions. Spray the top and bottom grates liberally with nonstick spray or melted butter. Remove the French toast from the eggs using a slotted spatula, allowing excess egg mixture to drip off. Make 2 at a time on the diagonal of the grates. Press down gently at first, then add a little pressure to the cover and press until the cover is completely closed. Cook until golden brown, about 3 minutes. Repeat with the remaining 6. Carefully remove each French toast waffle to a plate.
Schmear each waffle with peanut butter. Dust with confectioners' sugar and drizzle with some of the mixed berry syrup. Garnish with fresh mixed berries, berry syrup, banana slices and mint sprig.
Mixed berry sauce:
Combine the strawberries, blackberries, raspberries, sugar and 1/4 cup water in a medium saucepan, bring to boil and cook, stirring occasionally, until the berries are soft, about 10 minutes. Remove from the heat and let cool for 5 minutes.
Transfer the berry mixture to a blender or food processor, add the raspberry preserves and lemon juice and blend until smooth. Transfer to a bowl and let cool to room temperature. The sauce will keep in the refrigerator stored in a container with a tight fitting lid for 1 week.
Cook's Note: Use leftover sauce drizzled over pound cake, ice cream or frozen yogurt.