Combine the strawberries with the granulated sugar in a medium bowl and stir to combine. Place in the refrigerator to chill for at least 1 hour, or overnight to allow them to macerate.

Beat the eggs well in a shallow, large baking dish. Add lemon zest, cinnamon,  buttermilk, and vanilla. Beat to combine.

Coat the surface of a large frying pan and add 1 tablespoon butter. Place over medium heat and allow butter to melt, tilting the pan to coat.

Soak two slices of bread in the egg mixture, flipping once, until drenched, about 1 to 2 minutes per side. Transfer to the hot pan.

Cook until browned on one side, about 2-3 minute per side. Using a spatula, flip bread over and repeat with the other side. Add 1 Tbsp butter to the pan between each set of slices and repeat the process of soaking the bread and cooking it. Continue with the remaining bread until finished.

In a medium bowl, combine mascarpone cheese, powdered sugar, and chocolate chips stirring until well combined. Drain the chilled strawberries of any liquid and add to the bowl. Mix gently to incorporate.

Spread 1/2 cup of the strawberry filling between two slices of cooked French toast. Repeat with remaining filling and French toast slices.

Dust with powdered sugar, and serve.