Preheat oven to 350 degrees. Line an 8" square pan with parchment leaving an overhang on two sides.

In a large mixing bowl, combine 3/4 cup flour, corn starch, icing sugar and 1/2 teaspoon of salt. Add butter and lavender and work with your fingers until mixture resembles coarse crumbs. (You can also use a food processor for this step, but I prefer the hands-on approach).

Transfer mixture to prepared square baking pan and press down firmly on the bottom and about 1/2 inch up the sides. Bake for 20 to 25 minutes, until golden brown.

Meanwhile, add the granulated sugar, eggs and egg yolks to the bowl of electric mixer and beat until it is a pale yellow colour. Add lemon juice, zest, remaining 1/4 cup flour and 1/4 teaspoon of salt and mix just until well combined.

Pour filling over the warm crust and bake until set, about 20 minutes.

Remove pan from oven and cool on wire rack until room temperature. Then refrigerate for a minimum of 1 hour.

To serve, remove the squares from the pan by lifting with the parchment paper overhang, slice and sprinkle with a bit of additional icing sugar.