Chop sweet potatoes into large chunks, and the plantains into rounds, slightly bigger than the sweet potatoes since they roast slightly quicker.
Season the veggies with grapeseed oil and salt.
Place into the air fryer and roast for 20 minutes at 450 degrees.
Take the tray out to flip them then roast for another 20 minutes.
Remove from the air fryer and place into a bowl. Using a potato smasher, mash the veg into your preferred texture. Mash longer for a smoother mashed potato like texture or leave chunkier for more bite.
Pour into molds and freeze at least overnight.