In a small saucepan, melt the butter over low heat.Add a tablespoon or two of the melted butter to the cold milk to temper it. Please do this step. If you don’t? You’ll cause the milk to curdle.Add the remaining butter to the milk and return to low heat. Cook on low heat and stir with a whisk until the mixture is hot and well combined.Add to a mixing bowl or blender and mix under thick.Store in an airtight container in the fridge for up to a week.