Pierce the sweet potatoes all over with a fork, place directly on to a microwave plate and cook for 10 minutes till very soft. You can also do this in the oven.
Take out and leave to cool enough so they can be handled and then scoop out all the flesh and pop into a bowl. Mash to a smooth paste with the cinnamon, orange zest and walnuts. Set aside.
For the pastry, pop the butter into a pan and melt till brown. As soon as it starts to bubble and brown flecks appear, you have browned the butter. Take off the heat.
Preheat the oven to 190°C and have a baking tray at the ready.
Cut the filo sheets down the length and create 14 strips of filo, leaving the sheets you’re not working with under a damp tea towel. Butter two sheets together. Take a dollop of the filling and place at the bottom of the end of the strip. Fold a corner over to create a visible triangle, encasing the filling. Now take the filled triangle and fold over again and keep going till you have a fully encased triangle. Make the other six and butter them all over with any leftover butter.
Pop on to the tray and bake for 20 minutes.
Make the syrup by pouring the orange juice into a pan with the water and caster sugar. Bring to the boil and leave to simmer till the syrup is thick and golden.
Take the triangles out of the oven and dip straight into the syrup till completely coated, then coat with pistachios and set aside.
For the strawberry coulis, put the fresh strawberries, icing sugar and lemon juice in a food processor and blend. Serve alongside the samsas as a dip or a drizzle.