For the dough, dissolve baking soda in 3 tablespoons of warm water in a mixing bowl. Add oil, milk, egg, sugar and 450 g flour. First mix with the whisks of the mixer until crumbly, then knead with your hands to a smooth, elastic dough.
Place on a plate, cover with the mixing bowl and leave to rest for about 1 hour.
For the filling, meanwhile, chop the trail mix and candied orange peel in the universal chopper. Bring honey to the boil with 100 ml water while stirring, simmer for about 8 minutes at medium heat. Remove from the heat, stir in the nut mixture and let it cool down.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Roll out dough 2-3 mm thinly on a floured surface. Place just under 1 tsp. of filling next to each other on one half of the dough with a good finger width apart.
Place the other half of the dough on top. Press the dough firmly between the individual piles with your fingers (if air is trapped, prick with a small wooden skewer). Cut out round piles (approx. 5 cm Ø).
Press together well all around the edge with a floured fork.
Place on a baking tray lined with baking paper. Bake in a hot oven for about 20 minutes. Remove and dust immediately with icing sugar. Let it cool down.