Make the base: Pre heat oven to 180ºC (fan forced) and grease and line a 20 x 20cm square baking tray with baking paper, leaving some overhang.
In a large bowl, mix together the softened butter, caster sugar and vanilla, mix well with a rubber spatula.
In another bowl, combine plain flour, almond flour and salt. Add the dry ingredients to the butter mixture and knead well until you get a homogenous cookie dough mixture.
Take out 1/3 of this cookie dough and set it aside. Press the remaining 2/3 of dough into the lined baking tray and smooth it out into an even layer. Set aside.
Make the Almond filling: in a medium size bowl, mix together the softened butter, sugar, vanilla and almond extract until well combined and smooth. Add condensed milk and mix again (but don’t whisk it or overmix).
Add the almond flour and milk and mix until you get a thick spreadable consistency.
Dollop the almond filling over the top of the base prepared in step 1. and spread it out to an even layer all the way to the edges of the tray.
Make the Crumble Topping: Crumble the remaining dough over the top of the almond filling.
Sprinkle evenly with flaked almonds and bake in the oven for 30-35 minutes until the top is a deep golden brown.
Remove tray from oven and allow to cool completely on the bench before sprinkling generously with icing sugar. Cut into squares and serve.