Add the maple syrup to a heavy bottomed pot that holds about 4 cups (enameled cast iron works great). If you have a candy thermometer with a clip, attach it to the side of the pot.

Bring the maple syrup to a boil over medium heat and keep boiling until it reaches 230 F, roughly 10-15 minutes. Do not stir during this time, to prevent crystallization.

No thermometer? Drop a spoonful of the hot caramel into a bowl of ice water. If it forms a pliable soft ball, it's around 240 F; a hard ball means 250-260 F.

Remove the pot from the heat. Add the oat milk, vanilla, and salt and stir gently, stopping as soon as everything is combined. Don't over-mix.

Let the sauce cool in the pot for a few minutes, then pour into a heat-safe glass jar. Let it cool at room temperature, then cover. It thickens as it cools; you may also chill it.

Serve cold, or warm in the microwave for 20-30 seconds. Keeps for 1 week refrigerated.