In a small bowl, mix the plant-based milk with apple cider vinegar and let it sit for 5 minutes to curdle (this creates vegan buttermilk).
In a large mixing bowl, whisk together the dry ingredients: flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
Add the sugar, oil, vanilla extract, and vegan buttermilk to the dry mixture. Mix until you form a smooth dough.
Shape and Cook
Roll out the dough on a lightly floured surface to about ½ inch thickness. Use a doughnut cutter or two circular cutters (one large, one small) to shape the doughnuts.
Heat oil in a deep pan to 350°F (175°C). Carefully fry the doughnuts in small batches for 1-2 minutes on each side until golden brown. Transfer to a plate lined with paper towels to drain excess oil.
Make the Glaze
In a small saucepan, gently warm the Biscoff spread until it becomes runny.
Remove from heat and whisk in the plant-based milk and powdered sugar until smooth.
Glaze and Garnish
Dip each cooled doughnut into the Biscoff glaze, allowing the excess to drip off.
For added crunch and visual appeal, sprinkle crushed Biscoff biscuits on top.