Dissolve yeast in 300 ml of lukewarm water. Mix 500 g flour, sugar and salt in a mixing bowl. Add yeast and oil and knead with the dough hooks of the mixer. Cover and leave to rise overnight in the refrigerator.
Knead the dough again on some flour and form with floured hands about 12 longish rolls (about 10 cm). Put them on a baking tray lined with baking paper and let them rise for another 30 minutes.
Whisk the egg yolk and 2-3 tablespoons of water. Spread the bread rolls with it. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for 20-25 minutes. Let them cool down. With banderoles as desired