Cook's Note: Mascarpone is similar to cream cheese in flavor (but better) and has the consistency to match. It makes a great base for this super-easy yummy filling.
Combine the mascarpone, heavy cream, orange zest and sugar in a bowl. Add the melted chocolate and mix until all the ingredients are incorporated. Using an offset spatula or butter knife, take a generous scoop of the chocolate-mascarpone filling, about 2 tablespoons, and slather it on 1 slice of the brioche, and then top with another slice of brioche. Repeat with the remaining slices and filling; you will make 6 sandwiches.
In a shallow dish, whisk together the eggs and half-and-half to make an egg bath. (If you don't have half-and-half, milk or heavy cream will work just fine.)
Preheat the oven to 200 degrees F.
Preheat a nonstick griddle or large skillet over medium heat. Add 1 tablespoon butter to the skillet, moving it around to coat the surface. Dip each sandwich in the egg bath, turning over to coat and soak both sides. Place the sandwich on the hot griddle. (Place only as many sandwiches as will fit easily on the griddle, don't overcrowd.) Cook, in batches, until golden, 2 to 3 minutes per side. Transfer the sandwiches to an oven-safe platter and cover loosely with foil. Place in the oven to keep warm. Add more butter to the griddle, as necessary, and cook the remaining sandwiches.
Cut the sandwiches diagonally in half, and serve 2 to 3 halves per person. Dust the sandwich with confectioners' sugar and grate chocolate over the top. Ladle a generous portion of the Strawberry Syrup over the sandwiches, or serve alongside for your guests to serve themselves.
In a large saucepan over high heat, add the strawberries and sugar. (A large saucepan is needed just in case the strawberry syrup starts to boil up the sides.) If the strawberries are not as ripe or sweet as you like, add 1/3 cup more sugar. Add 2/3 cup water, the corn syrup and sea salt to the pan. Stir together until the sugar dissolves. Bring to a boil and cook for about 5 minutes, stirring occasionally.
Strain out the strawberries and continue to boil the liquid until the mixture has thickened to a syrupy consistency, another 8 to 10 minutes. Stir in the lemon juice and add the strawberries back to the saucepan. Gently stir to coat the strawberries in the syrup. (The syrup can be stored in an air-tight container in the refrigerator for up to 1 week, or cooled and frozen.)
Cook's Note: For an orange-lover's option, use fresh orange juice instead of the lemon juice to finish the syrup. Alternately, for a rich, adult-friendly sauce, add a splash of orange liqueur, like Grand Marnier, to the sauce. Although the alcohol won't completely cook out, most will if cooked a few minutes longer. Yield: 3 1/2 cups