Preheat the oven to 200°C (approximately 400°F) convection.
For the cookies, separate the eggs. Beat the egg whites with the salt until stiff. Beat the yolks with the sugar until thick and creamy. Add the egg whites to the egg yolk mixture, sift in the flour, and gently fold until combined. Spread the batter evenly on a parchment paper-lined baking sheet. Bake in the oven for about 12 minutes. Turn out onto a tea towel sprinkled with sugar, remove the parchment paper and allow to cool (about 1 hour). Cut out about 12 hearts (about 10 cm (approximately 4 inches) in diameter) cut out. Spread half of the hearts with jam and top with a second heart on it. Sprinkle with powdered ugar and serve garnished with daisies.