1. Sift the flour,sugar,baking powder,baking soda and salt into a large bowl. Add the lime zest and butter,then rub together to flatten the pieces of butter so they form small flakes. (You could also do this in a food processor.)
2. Lightly whisk the egg and creme fraiche together in a bowl,then pour into the flour mix. Use a rubber spatula to fold together until the mixture forms a shaggy mass,then turn it out onto a floured workbench and roll the dough into a (roughly) 30cm square. Using a pastry scraper to help you,fold it into thirds. You now have a long rectangle about 10cm x 30cm. Lift the short ends of the dough and fold into thirds again,forming a small square. Dust with flour,transfer to a plate and refrigerate for 10 minutes.
3. In the meantime,hull the strawberries,cut into pieces about 1cm in size and set aside.
4.Preheat the oven to 210C (190C fan-forced).
5.Roll out dough onto a floured workbench (it will be very soft,so roll gently) into a 30cm square. Scatter the strawberries evenly over the square,then,using the pastry scraper to help you,roll it up,Swiss-roll style,so it forms a log. Lay seam-side down and gently squeeze or pat the log to make it an even thickness. Using a sharp,floured knife,cut into it 3 to 4-centimetre rounds. Place flat on a baking tray lined with baking paper.
6. For the topping,combine the sugar and lime zest in a small bowl and rub together to release the citrus oils into the sugar. Brush the top of each slice with milk or creme fraiche and sprinkle liberally with the lime sugar.
7.Bake until the tops and bottoms are golden brown,about 25 to 30 minutes.
8. Transfer to a cake rack to cool for 10 minutes before serving.
Tip:Leftover scones may be reheated in a warm oven for 5 minutes.