In a mixing bowl, whisk together the all-purpose flour and granulated sugar. Create a well in the center and add the eggs. Slowly pour in the milk while whisking continuously until the mixture is smooth. Stir in 4 tablespoons of melted butter and the vanilla extract. Let the batter rest for about 30 minutes at room temperature.
Heat your non-stick skillet over medium heat and lightly grease it with a small amount of melted butter. Pour about 1/4 cup of batter into the skillet, swirling it around to cover the bottom evenly. Cook for about 1-2 minutes, or until the edges begin to lift and the bottom is lightly golden. Carefully flip the crepe and cook for another minute on the other side. Repeat this process until all the batter is used, stacking the crepes on a plate as you go.
In a saucepan over medium heat, melt 4 tablespoons of butter. Add the brown sugar and stir until it dissolves completely. Squeeze the juice of 2 lemons into the mixture, stirring until it thickens slightly. Add a generous pinch of sea salt and mix well.
To serve, place a crepe on a plate and drizzle with the salted lemon butter caramel. Fold the crepe in half, then in half again to form a triangle. Drizzle more caramel over the top, and garnish with fresh mint or thyme.