Boil two pans of water. One for the potatoes and one for the eggs and salt the water that the potatoes are going in.
Carefully place the potatoes in the salted water and the eggs in the other pan and simmer them both on a high heat until cooked through. Drain and set aside to cool
Melt the butter in a large frying pan for the herring to cook in. I like to use my cast iron gridle on a medium heat.
Wash and dry your herring fillets if nessecary. You want them as dry as possible so use kitchen towel if you need to.
Pour out your oatmeal into a small shallow dish. Season well with salt and pepper and mix through.
Place a fillet of herring into the oatmeal and press down gently. Sprinkle the top of the herring to ensure the herring is well covered in the oatmeal. Turn the fillet over and repeat on the other side.
Turn the fillets several times in the oatmeal until there is a good quantity of oatmeal attached to the herring fillet and it can't hold any more.
Place the herring fillet skin side down into the pan and cook in the melted butter gently for 4-5 minutes. Flip around to the other side for another 4-5 minutes.
Lift out of the pan and repeat with the other fillet and any others you are cooking.
Chop the cooked potatoes into small cubes and peel and chop the eggs into a similiar size. Add the mayo and mix around gently. Sprinkle in the spring onions and herbs and season with salt and pepper.
Serve the cooked herring alongside the salad and add in any additional salad items like greens or some sliced/ tomato. Enjoy!