Preheat oven to 200°C. Place oven rack in the middle of oven.
Sift together flour, salt, baking powder and castor sugar into a mixing bowl. Place in a food processor with the butter and orange zest. Process until it resembles fine breadcrumbs, then empty this back into the bowl.
Mix in about 3/4 cup cream, just until most of the dry ingredients have been moistened. Turn out onto a floured board and knead gently until the dough just comes together. Don’t overwork it.
Roll dough out to 1.5 centimetres thick. Using a 7-centimetre diameter cutter, cut out shortcake rounds. Lightly knead together remaining dough, re-roll and cut out until all used. Place on a tray lined with baking paper. Brush tops lightly with some cream. Bake for 10-12 minutes, until the tops are light brown and the dough is set.
Wash, dry and hull the strawberries. Using a mortar and pestle, lightly crush about a quarter of the strawberries. Place these in a bowl. Slice the remaining berries and add to the bowl with 2 tbsp icing sugar. Mix through and chill in the fridge until ready to serve.
Place remaining cream in a bowl with the vanilla paste. Sift in 2 tbsp icing sugar and whisk until soft peaks form.
Split the shortcakes in half. Place some cream and strawberries on each base, then finish with the shortcake tops.