Make the crepe batter: In a mixing bowl, whisk together the flour, cocoa powder, sugar, and salt. In another bowl, whisk together the milk, eggs, melted butter, and vanilla extract. Gradually add the wet ingredients to the dry ingredients, stirring until smooth. Let the batter rest for about 15-30 minutes.

1. Cook the crepes: Heat a non-stick skillet or crepe pan over medium heat. Lightly grease the pan with butter or oil. Pour a small amount of batter into the center of the pan, tilting the pan to spread the batter into a thin, even layer. Cook for about 1-2 minutes on each side, or until the crepe is lightly golden. Remove the crepe from the pan and set aside. Repeat with the remaining batter, greasing the pan as necessary.
2. Prepare the chocolate filling: In a small saucepan, heat the heavy cream over medium heat until it begins to simmer. Remove from heat and add the chopped chocolate and butter. Stir until smooth and the chocolate has completely melted. Let the chocolate mixture cool slightly.
3. Assemble the crepes: Place each crepe flat on a plate. Spoon a generous amount of the chocolate filling onto the center of each crepe and spread it evenly. Fold the crepes into quarters or roll them up, depending on your preference.
4. Prepare the strawberry topping: Toss the sliced strawberries with sugar, if desired, and let them sit for a few minutes to release their juices.
5. Serve: Arrange the filled crepes on a serving plate. Top with the sweetened strawberries and drizzle any remaining chocolate filling over the crepes. You can also garnish with whipped cream, chocolate shavings, or a dusting of powdered sugar if desired.