Cut margarine into flour with two knives or a pastry-cutter. Sprinkle water on top and with floured hands, gently squeeze into a ball. Refrigerate for 30 minutes before rolling out on a floured surface.
Wash and trim rhubarb; chop into 1 cm/1/2-inch slices. Sprinkle with salt; let stand about 20 minutes. Wash and hull strawberries; cut larger ones in halves or quarters.
Roll out pastry and cut out pie lid; roll out remaining pastry and line bottom and sides of pie pan.
Stir strawberries and rhubarb together; stir in sugar, flour, and a pinch of ginger if you like ginger. Scrape mixture into pan; top with pastry lid. Crimp edges and cut vents.
Place pie on a baking sheet to catch drips. Bake in 200°C / 400°F oven for 45-55 minutes - until filling is bubbling and pastry is golden.
Where I live, most soft margarine comes salted, so I don't add any salt - adjust to your own preference and ingredients.
• Please note that the nutrition information provided below is approximate and meant as a guideline only.
• Unless stated otherwise cup conversions have been made with an online tool. For accuracy please check with your favoured conversion tool. We recommend buying inexpensive digital kitchen scales.