Mix the flour and sugar in a bowl. Cut the butter into pieces, add to the bowl, rub together using your hands to form an even, crumbly mixture. Roll out the dough between a cut-open plastic bag to a thickness of approx. 2 mm, chill for approx. 30 mins.
Beat the egg whites and salt until stiff using the whisk on a hand mixer, gradually add the sugar, continue to beat briefly. Mix the nuts into the egg whites in stages. Cut out 4 turtles with heads and legs (each approx. 6 cm in diameter), transfer to a baking tray lined with baking paper. Spread the jam in the middle.
Cut 4 circles (each approx. 8 cm in diameter) out of the chilled dough and place on the body of each turtle.
Approx. 20 mins. in the centre of an oven preheated to 180°C.
Add sugar eyes to the heads using writing icing.