First prepare the crumble. In a bowl mix together the sugar, flour and zest of one lemon. Put in small cubes of softened butter and lightly rub into the flour mixture using your fingertips until there are no more big lumps of butter. Knead to form a bowl. Wrap the dough in a plastic wrap and put in a fridge for 2 hours.
Preheat the oven to 200°C / 395°F. Grate the crumble dough with a grater, using the side with the largest holes. Place it all over a baking tray, lined with parchment paper. Lower the oven temperature to 190°C / 375°F and bake for 8 minutes. Take it out of the oven, slice it the way you need it. We used a round pastry ring for our dish and bake it again for 3 - 4 minutes, until golden. Let it cool for about 10 - 15 minutes.
Wash the strawberries and cut the tops with green leaves off. If you have bigger strawberries, cut them in half. Put the strawberries in a bowl, sprinkle them with sugar and 1 tbsp of lemon juice. Gently combine with a spoon, so that the sugar dissolves completely, add the mint or citron verbena or both. Set aside until needed.
Take your rhubarb granita out of the fridge, crush it, so that you get small chunks and blend it right away, so that it becomes smooth and silky, like an icecream. First blend on a maximum speed for about 10 seconds, stop and repeat the process until you get a silky sorbet.
Fill your plates with marinated strawberries, then place pieces of crumble on top of it and finish with a nice, silky scoop of rhubarb sorbet. Enjoy.TipTo get a nice, smooth shape of the sorbet, place a spoon under a hot running water and scoop the sorbet out of the bowl.