Scottish tablet frozen yogurt

Grease a 20cm x 20cm shallow square tin.

Gently melt the butter in a large, heavy-based pan. Add the sugar and milk and simmer on low, stirring, until the sugar dissolves. Add the condensed milk, bring to a boil and simmer for 5-10 mins until thickened, stirring continuously.

Test the temperature of the mixture with a sugar thermometer. Once it reaches 115C, remove from the heat. Beat with an electric hand-whisk, on a slow speed, for 5 mins until thickened but still liquid enough to pour. Transfer to the tin. After 15 mins, score the top to make it easier to break. Cool, then snap into pieces.

Blend the yogurt and 1⁄4 of the tablet in a processor until smooth. Pour into a lidded, plastic container and freeze for 2 hrs, then blend again to break up the ice crystals. Freeze for 1 hr. Blend twice more, returning the mixture to the freezer each time.

Remove from the freezer 20 mins before serving and sprinkle with a little more tablet. The remaining tablet can be stored in an airtight container in a cool, dry place for up to 1 month.