Preheat the oven to 180C / 350F / 160C fan forced. Line an 8 inch square baking tin with baking paper.
Sift together the flours and set aside.
Beat together the butter and sugar until light and creamy, scraping down the sides of the bowl as necessary.
Gradually add the flour mixture while continuing to beat on low until it comes together.
Use your hands to press the shortbread mixture into an even layer over the base of the baking tin.
Bake for 20 minutes.
FOR THE FILLING
Whisk together the condensed milk, lemon juice and passionfruit pulp then pour over parbaked base.
Bake for another 15 minutes until firm then allow to cool before adding the topping.
FOR THE TOPPING
Place the strained passionfruit pulp in a small saucepan and sprinkle the gelatine evenly over the top. Let it sit for 5 minutes to soften.
Turn the heat on low and stir until the gelatine has dissolved.
Add the sugar and stir until dissolved. Don't let it come to a bubble, it should be just hot enough to dissolve the sugar.
Add the water and add back 1 teaspoon (or to your taste) of the seeds. Mix well and carefully pour the topping over the slice.
Leave to set for at least 2 hours before cutting and serving.
Equipment: 8x8 inch square baking tin
For best results you should always weigh ingredients like flour and sugar. Kitchen scaleslike these are relatively cheap but if you can’t weigh the ingredients, use the spoon and level method (don’t scoop).