Preheat your oven to 350 degrees Fahrenheit or 180 degrees Celsuis (fan oven) and butter and flour or grease and line a baking sheet with parchment paper. I use a 9.5x11" baking dish but you can use something slightly smaller or larger.
In a mixing bowl, add the berries, 1.5 tbsp white sugar, vanilla and cointreau (if using) and stir to completely coat the berries. Set aside.
In another mixing bowl, combine everything except the butter and stir to combine. Add the butter and incorporate it into your 'dough' with your hands, crumbling it until the ingredients have just come together. If your butter is too soft, it won't crumble, so make sure its just soft enough to work with without being too malleable.
Press 3/4 of the dough into the bottom of your baking dish. Add the fruit. Top with the remaining dough. Dot with a few pads of butter, if you like.
Bake for 45 minutes, or until the top is golden brown and the fruit is bubbling.
Allow the pan to cool COMPLETELY before slicing. If you try to cut these before they're cooled, they'll still taste incredible, but they'll be more 'crisp' than 'bar.'
I like to eat mine at room temp with some tea or coffee, or warmed up with vanilla ice cream as a treat after dinner. Enjoy!