Yes, you can store it in the fridge but be aware that the dry fruit paste turns rancid very fast. I would refrigerate it for up to 2 days. If you want to store the nuts for longer then soak the almonds, cashews, pistachios, in water for a few hours. Drain all the water and let them dry naturally. Make a powder by blending or crushing the dried nuts. You can then refrigerate or freeze the powder. When making the milkshake, blend the ground nuts powder, dates, figs, raisins with the milk or you can make a simple drink by warming or heating the milk with the nuts powder adding a sweetener like raw sugar or maple syrup. You can also make almond powder by blanching the almonds in hot water for 30 minutes, peeling their skins, drying them and later blending or crushing them. Blanching and peeling almonds help to aid their digestion.