Finely grate the Gruyère and Parmesan cheese. Mix 125 g flour and baking powder in a bowl. Add cheese and butter in pieces. Knead first with the dough hooks of the mixer, then with your hands briefly to a smooth dough.
Cover and chill for about 30 minutes.
Cut the dough in half. Form each half on a little flour first into a roll (approx. 35 cm long), then use a ruler to form a square stick. Turn one stick into poppy seed and press it down lightly.
Turn the second bar in sesame seeds and press lightly. Put both sticks in a cool place for about 1 hour.
Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Line two baking trays with baking paper. Cut the sticks into slices just under 1 cm thick and spread them on the baking trays.
Bake in a hot oven for 8-10 minutes. Pull the crispy cubes and paper from the baking tray and let them cool down. Bake the remaining dough squares in the same way.