Sift the dry ingredients into a bowl. Cut the cold butter into small pieces and mix with a scraper until crumbly.

Add the cold milk and egg to the mixture and combine gently.

Fold in the dried blueberries and chopped walnuts, mixing lightly with a knife.

Place the dough in a plastic bag and refrigerate for 30 minutes.

Roll the dough out with a rolling pin, perform a three-fold, and shape into a rectangle. Cut into squares using a knife.