Preheat the oven to 375°F (190°C), place the chicken on a rack set over a rimmed baking sheet, and roast for 35 to 40 minutes until cooked through. The chicken should feel firm, the juices should run clear, and it should reach 165°F for proper doneness.

Let the chicken cool enough to handle, then pull the meat from the bones with forks and shred it into a bowl. You want bite-size shreds that mix easily into the filling without clumping.

Whisk the flour and salt together in a large bowl, then pour in the milk gradually while whisking so the batter stays smooth. The mixture should loosen steadily and look silky rather than pasty or lumpy.

Whisk in the beaten eggs, then add the melted butter and fresh dill, and let the batter rest for at least 30 minutes. After resting, the batter should look like heavy cream and pour easily.

Heat a non-stick 12-inch (30 cm) skillet over medium-high heat and lightly grease it with oil on a paper towel. When the batter hits the pan, you should hear a soft sizzle right away.

Pour in one ladle of batter and immediately swirl the pan so the bottom is covered in a thin layer. Cook until the surface looks set and the edges turn lightly golden.

Slip a thin spatula under the crepe, flip it quickly, and cook the second side for 30 seconds more. The finished crepe should be flexible with a few pale golden spots, not crisp.

Transfer each crepe to a cutting board and continue until all the batter is used, then let the stack cool while you make the filling. Cool crepes are easier to fill and less likely to tear.

Melt the butter in a large skillet, add the leeks, and cook until soft and fragrant before adding the mushrooms, Worcestershire sauce, salt, pepper, and parsley. The vegetables should look tender and lightly glossy, with most of the moisture cooked off.

Melt the butter for the sauce in a deep skillet, whisk in the flour, and cook briefly until a smooth paste forms. The roux should look like pale sand and smell buttery, not browned.

Pour in the milk slowly while whisking, then simmer until the sauce thickens before stirring in the garlic, salt, and pepper. The Béchamel is ready when it turns smooth, velvety, and coats the back of a spoon.

Set one crepe in a small gratin dish, add 2 tbsp (30ml) mushroom filling, ¼ cup (30g) shredded chicken, and 2 tbsp (30ml) Béchamel, then roll it up and spoon more sauce over the top. Finish with Gruyere and paprika, making sure the crepe is lightly covered so it stays moist in the oven.

Bake the filled crepes at 350°F (175°C) for 10 to 12 minutes, then broil for 1 to 2 minutes and garnish with parsley before serving with the salad. The top should be bubbling at the edges with golden spots of melted cheese.