Make the crumble topping: Mix the cashew butter and honey/maple syrup in a bowl. Add a splash of milk to thin.
In another bowl, mix the oats, ground almonds, flaxseeds, and pinch of salt.
Add the nut butter mixture into the oat mixture and mix until evenly coated to form clusters.
Make the yoghurt layer: In another bowl, mix the Greek yoghurt, lemon zest, lemon juice, vanilla extract, protein powder and sweetener of choice.
Assemble the jars: Using 4 jars, add 80g frozen berries with 1 tsp chia seeds to the bottom of each jar.
Divide the yoghurt mix evenly onto the berries.
Top with the crumbly topping.
Leave in the fridge to set overnight.
