Preheat oven to 350

For the jam, put blueberries and sugar in a medium sized saucepan, add lemon juice at this stage as well

Stir this mixture on medium low heat until it begins to bubble. to your blueberry jam, add mixture or corn starch + water while it is continuing to boil

Let this simmer on medium low heat (mix every minute or so) for 3-4 minutes

For the shortbread, in a separate bowl, mix your butter with a whisk until it turns an off white color

Add your sugars into butter and mix until fluffy

Add vanilla, lemon extract, and lemon juice to this mixture

Add salt and flour until well combined

Butter a 9x9 square pan and flatten about 3/4 of your dough into a pan and add blueberry
mixture on top

Add extra dough crumbles on top of blueberry spread, and put in the oven for 42-44 minutes

Let cool and add powdered sugar to top (optional)