Put milk and peppermint leaves in a blender, blend until smooth and pour through a fine sieve.
Mix 125 g flour, sugar and salt in a mixing bowl.
Pour the peppermint milk into a saucepan and bring to a boil very briefly.
Pour the hot peppermint milk into the mixing bowl with the flour mixture, mix thoroughly with a whisk to form a homogeneous mixture and leave to cool to lukewarm.
Add vegetable oil and egg to the peppermint mixture and stir to combine.
Mix the remaining flour with baking powder.
Add the flour mixture in portions to the liquid peppermint mixture and knead briefly to form a soft, slightly sticky dough.
Cover the dough and leave to rest at room temperature for 20 minutes.
Roll out the dough on a well-floured work surface to a thickness of approx. 1 cm - 1.5 cm and cut out round cookies.
Spread the peppermint pryaniki on a baking sheet lined with baking paper, bake in a preheated oven at 356 °F (180 °C) for approx. 15 - 20 minutes and leave to cool.