Add the pata kūteretere (softened butter), huka hāura (brown sugar), wanira (vanilla) and kiri rēmana pīrahirahi (finely grated lemon zest) in to a large bowl. Whip on high for 3-4 minutes until fluffy and creamy.
Add the hēki (egg) and whip for 30 seconds.
Add in the kokonati pūtī (desiccated coconut), puehu parāoa noa (plain flour) pēkana paura (baking powder) and ōti (oats) in to the butter mixture. Stir well with a wooden spoon.
Add half the oat mixture in to the base of the prepared tin and press it down firmly with the back of a spoon. Take the time to press it well in to the corners of the tin. Add the cooled berries and the jam on top.
To the second half of the oat mixture, add the extra ½ C ōti (oats) and mix with a spoon. Sprinkle this over the top of the berries in big clumps.
Add the cup of reserved hua tio (frozen berries) in the gaps of the oat crumble.
Bake for 50 minutes until golden.
Plain option: Remove it from the oven, allow to completely cool and cut in to desired pieces. Fancy Slice option: Remove it from the oven, allow to completely cool. Drizzle with:50 g tiakarete mā kua rewaina (melted white chocolate) And a handful of rōpere tauraki-tio (freeze-dried strawberries)Chill it for 10 minutes or until it is set and cut in to desired pieces. Dessert option: Allow the slice to cool in the tin 10 minutes or so. Slice in to desired pieces and add to plates. Top with aihikirīmi (ice cream) and eat warm as the aihikirīmi drips over the delicious slice.