Remove the strawberries from the freezer and set them aside in a bowl to thaw.
In a large mixing bowl, sift together the flours and caster sugar.
Cut the butter into small cubes after removing from the fridge. Immediately add these to the mixing bowl.
Using a rubbing action with your fingertips, rub the butter into the flour and sugar until a rough dough forms.
Add in the first tablespoon of ice cold water and knead the dough in the bowl until a ball forms. If it is still breaking apart or not very workable, add the other tablespoon of water and knead it in.
Place the dough in the fridge for 30 minutes to chill.
Preheat the oven to 180 degrees Celsius and line a standard baking tray.
If not already sliced, slice the strawberries roughly and return them to the bowl.
Add the caster sugar and cornflour to the bowl with your strawberries and toss them through until evenly coated.
Once your dough has chilled, place it on the baking tray and, using a rolling pin, roll it out until it is around 1/2cm thick. Rustic edges are absolutely fine.
Put the strawberry mixture onto the base but leave around 2-3cm of bare dough around the edge.
Fold the edge in sections towards the middle of the galette to cover the edges of the filling. Repair any breaks in the dough by pushing it together with your fingers.
Bake in the oven for 40 minutes or until golden brown.