Heat the oven to 160°C/140°C fan/gas mark 3. Whisk the milk, eggs, vanilla, spices and baking powder together until well combined. Heat a waffle iron and grease with the spread. Soak four halves of the buns in the egg mixture for about 10 seconds each until the liquid is absorbed but the bun isn't falling apart.
Put each half into the waffle maker (you may need to do this in batches depending on the size of your waffle maker) and cook for 4-5 minutes until crisp. Repeat with the remaining bun halves. Put the cooked waffles onto a tray lined with non-stick baking paper and keep warm in the oven while you make the second batch.
Serve the waffles with fresh fruit, yogurt or your favourite a topping.