Preheat your oven to 400F and line a baking tray with parchment paper or a silicone mat.
Wash the sweet potatoes, but do not peel them. Piece the potatoes a few times with a knife, then place on the tray and bake for 45 to 60 minutes, or until a 'caramel' starts to ooze out of the pierced holes.
Remove the sweet potatoes from the oven, and carefully scoop out their flesh into a large bowl.
Add in the milk, flax, nut butter, vanilla, cinnamon, and salt.
Use a hand mixer to 'cream' the mixture together on for 60 to 90 seconds, starting with the lowest setting. Alternatively, you can place all ingredients into a food processor and blend until thick and smooth, 2 to 3 minutes.
Divide into serving bowls, top as desired, and serve warm. Leftovers will keep in the fridge for up to 5 days.
