Sweet Potato Doughnuts

Doughnuts

• 150 g sweet potatoes, peeled, cut in pieces
• 150 g water
• 40 g olive oil, plus extra for greasing
• 120 g granulated sugar
• 200 g whole milk
• 1 large egg
• 2 tsp vanilla extract
• 200 g plain flour
• 1 ½ tsp baking powder
• 1 ½ tsp ground cinnamon
• ½ tsp ground ginger
• ¼ tsp ground nutmeg
• 1 pinch fine sea salt

Topping

• 30 g pistachio nuts, unsalted, shelled
• 4 Tbsp icing sugar
• 2 tsp water, boiling