Preheat the oven to 200°C. Combine the grated sweet potato, sweetcorn, cornflour, spices and seasoning in a large mixing bowl. Melt small knobs of butter in individual blini pans until melted, then add large tablespoons of the mixture to the pans, pressing down well to create as even a surface as possible.
Flip after 2 minutes, then transfer to the oven and cook for a further 4-5 minutes until cooked through. Cook as many at a time as you feel comfortable doing. Remove once cooked through and turn out onto kitchen paper to drain. Cover with tin foil to keep warm as you cook the remaining rostis.
Arrange stacked on nonstick baking paper when ready to serve.