Make the crepe batter: In a medium bowl whisk together the all-purpose flour, granulated sugar and fine sea salt until evenly combined.

Add wet ingredients: In a separate bowl whisk the eggs, then whisk in the whole milk, water, melted butter and vanilla extract until smooth.

Combine and rest: Gradually pour the wet mixture into the dry ingredients while whisking to avoid lumps; the batter should be very thin and pourable. Cover and refrigerate for at least 30 minutes and up to 2 hours to allow the flour to hydrate and air bubbles to relax.

Prepare optional homemade chocolate-hazelnut ganache spread: Place the chopped dark chocolate in a heatproof bowl. Heat the heavy cream until it just begins to simmer, then pour it over the chocolate and let sit for 1 minute. Stir gently until glossy and smooth; stir in the hazelnut butter or paste if using. Let cool until slightly thickened but still spreadable.

Warm the pan and test: Heat a 9–10 inch nonstick skillet or crepe pan over medium heat until hot. Lightly brush with melted butter or oil. Pour a small spoonful of batter and tilt the pan to check how it spreads; adjust heat so the batter sets quickly but does not brown aggressively.

Cook the crepes: For each crepe, pour about 1/4 cup (60 ml) of batter into the center of the pan and immediately swirl the pan to create a thin, even circle. Cook 30–45 seconds until the edges lift and the underside is pale gold, then flip with a thin spatula and cook 10–20 seconds more. Transfer to a plate and cover lightly with a clean towel to keep soft. Repeat until batter is used, brushing the pan with butter between every 2–3 crepes if necessary.

Spread the filling: If using store-bought chocolate-hazelnut spread, stir it until smooth and slightly warm so it spreads easily. Lay one crepe flat, spread 1 to 2 tablespoons of filling in a line along one edge about 1 inch (2.5 cm) from the border. If using homemade ganache, use it once it reaches a thick but still spreadable consistency.

Roll the crepes: Tuck the edge of the crepe over the filling and roll tightly to form a neat spiral. Place the roll seam-side down on your serving board or plate. Repeat until all crepes are filled and rolled.

Make the drizzle: Place the chopped chocolate and neutral oil or 1 teaspoon extra melted butter in a small bowl. Microwave in 10-second bursts, stirring between, until smooth and pourable, or melt together using a double boiler. The oil or butter will create a glossy drizzle.

Finish the rolls: Drizzle the warm glossy chocolate across the rolled crepes in thin streaks using a spoon or a piping bag. Optionally dust lightly with powdered sugar and sprinkle a few flakes of coarse salt for contrast. Garnish with fresh berries or a dollop of whipped cream as desired.

Serve warm or at room temperature: These crepes are lovely immediately, or you can let the rolls rest for 10–15 minutes so the filling sets slightly and then serve. If you prefer a fully set center, chill the filled rolls for 20–30 minutes before serving.

Store leftovers: Refrigerate any leftover rolled crepes in an airtight container for up to 3 days. Before serving again, bring them to room temperature or gently rewarm in a low oven (300°F / 150°C) for 5–8 minutes, uncovered, to revive the crepe texture without over-softening the drizzle.