Place a small saucepan over a high heat and add an inch of water. Bring to the boil and then reduce the heat to low.
In a small bowl, whisk together the plant milk and the cornstarch. Set aside.
1 tablespoon plant milk, ¼ teaspoon cornstarch
Place the vegan mayonnaise and vegan butter in a heatproof bowl and sit it on top of the saucepan of simmering water. Whisk until the vegan butter is melted and the mixture is smooth.
60 ml vegan mayonnaise, 40 g vegan butter
Add the plant milk/cornstarch mixture and continue whisking until the mixture has thickened to a smooth, glossy sauce. Don't worry if the mixture appears to split, just keep whisking and the mixture will thicken.
Once the sauce has thickened, whisk in the remaining ingredients until smooth. Remove the bowl from the saucepan and serve warm.
1 teaspoon white wine vinegar, 1 teaspoon lemon juice, Pinch cayenne pepper, ⅛ teaspoon kala namak
Note: Store any extra vegan hollandaise sauce in a jar in the fridge. When you're ready to reheat the sauce, spoon it into a heatproof bowl and place over a pan of simmering water again. Whisk until smooth.