Puff pastry breadsticks with cheese

Ingredients:

• 1 sheet frozen puff pastry, thawed in the refrigerator
• 3 tablespoons Dijon mustard
• 1 egg, beaten with 1 teaspoon of water
• 80 g of grated Gruyere
• 2 tbsp. l. freshly grated parmesan
• Flour to dust the board
• Sea salt flakes, for sprinkling

Preparation:

1. On a well-floured board, unfold the puff pastry and roll it into a 27.5 x 32.5 cm rectangle, using a floured rolling pin. Roll diagonally to create a rectangular shape. With one short edge facing you, evenly coat the bottom half of the pastry with mustard, leaving a 1 cm border. Brush the edge of the pastry with beaten egg and fold the top half over the bottom, matching the edges. Place the pastry on a parchment-lined baking sheet and refrigerate for 15 minutes.
2. Place the dough on a board and trim three ragged edges with a sharp knife. The folded side of the dough should be facing away from you. Cut it into 2.5 x 15 cm strips. You will have 10-12 sticks. Arrange the sticks on a baking sheet, making sure they don't touch. Lightly brush the tops with beaten egg (the egg shouldn't run down the sides) and sprinkle evenly with Gruyere, Parmesan, and 1.5 teaspoons of sea salt. Refrigerate for at least 15 minutes.
3. Preheat oven to 200°C.
4. Bake the breadsticks for 15-18 minutes, until golden and puffy. Let cool on the baking sheet for 3 minutes and serve hot.