Preheat oven to 230 C/ 210 C fan and line a baking tray with a silicone baking mat or baking paper.
Sift together 425 grams self-raising flour, 1 tsp Shetland sea salt, and 60 grams caster sugar. Rub in 50 grams butter with your fingertips until it resembles coarse breadcrumbs.
Rub in 245 grams mashed potatoes until well combined.
Stir in 1 handful mixed herbs, finely chopped and make a well in the centre of the mixture.
Add 175 ml full fat milk and stir well with a wooden spoon until just combined.
Turn out onto a floured board and knead for a moment until smooth.
Cut into 8 even sized pieces and form into small round bannock shapes.
Cut a cross into the top of each bannock and bake for 20-25 minutes until golden on top. Transfer to a wire rack to cool completely. Store in an airtight container until needed.