Make a slit in the sides of each slice of bread to make a pocket that can be filled. Pipe or spoon 2 Tbsp. Nutella into center of each slice of bread through the slit. Place on a sheet pan, cover and refrigerate until ready to cook. In a bowl, whisk eggs until smooth, then whisk in milk and vanilla; cover bowl and refrigerate until ready to use. For Each Serving: Pour egg batter into a flat dish, lay a filled slice of bread in the egg batter and let soak. Turn and soak the other side of the sliced bread. Soaked bread should be slightly wet but not soggy or falling apart. Meanwhile, heat 2–3 Tbsp. oil in non-stick skillet over medium heat; place batter-soaked slice of bread onto hot skillet and cook 1 ½ minutes on each side, turning once, until each side is golden brown. Remove from skillet and place on a sheet pan and bake in 325°F convection or 375°F conventional oven for 5–6 minutes or until heated through completely. To serve, top each golden, hot piece of stuffed French toast with ¼ cup fresh berries. Serve immediately. Serve fruit preserves on the side, if desired.
