Assemble all the ingredients you need, wash the strawberries and pat them dry with kitchen paper towels.
With a knife, carefully remove the leafy parts of the strawberries, and pour them into a heavy-based saucepan. Add the sugar, pinch of salt, and vanilla essence.
Bring to a simmer with some water as you roughly crush the strawberries with a potato masher. Ensure you have some fruit lumps in the filling.
Lower the heat,in a mixing bowl mix the flour with water to make a slurry. Pour the flour mixture into the cooking strawberries. Stir vigorously for about two minutes.
The filling will begin to thicken,add a teaspoon of strawberry jello crystals. Stir until the crystals liquefy. Remove from heat and set aside to cool.
Once cooled, add lemon juice and mix thoroughly. This exquisite strawberry filling will enhance the overall taste of your cupcakes. Use the leftovers as a spread on toast or as pie or tart!