Method

• 1.
  Place sweet potato, aniseed, molasses and 300ml water in a saucepan over medium-high heat and bring to the boil. Reduce heat to medium-low and cook for 15-20 minutes or until sweet potato is tender. Strain, reserving 1/2 cup (125ml) cooking liquid. Cool cooking liquid to lukewarm, then stir through yeast. Set aside for 10 minutes or until frothy.
• 2.
  Meanwhile, place sweet potato in a stand mixer fitted with the dough hook. Add butter, cinnamon and 2 tbs caster sugar, and mash with a fork until smooth. Add flour and knead on low speed, slowly adding yeast mixture, for 10 minutes or until dough comes away from sides. Turn out onto a lightly floured work surface and knead to form a ball. Transfer to a bowl, cover, and set aside in a warm place for 1-2 hours or until doubled in size.
• 3.
  Knock back dough and divide into 10 even balls. Use your index finger to make a hole through each. Flatten slightly, then transfer to a baking tray lined with baking paper. Cover with a clean tea towel and set aside for 30 minutes to rise slightly.
• 4.
  Meanwhile, for the glaze, combine all ingredients in a bowl. Set aside.
• 5.
  To make mint sugar, place mint, lime zest and remaining 35g caster sugar in a small bowl and, using your fingertips, rub in to combine. Set aside.

• 6.
  Half-fill a large saucepan or wok with oil and heat to 170°C (a cube of bread will turn golden in 60 seconds when hot enough). In batches, add doughnuts and cook, turning halfway, for 4-5 minutes or until golden and cooked through. Drain on paper towel.
• 7.
  Dip doughnuts in glaze, then mint sugar. Serve warm.