Make the cashew butter: Place the honey in a microwave-safe container and heat in the microwave for 15 seconds. Remove from the microwave and add the oil. Place the nuts and salt in the bowl of a food processor and pulse for 5 seconds. Then, while the processor is running, very slowly drizzle in the honey and oil. Process until an emulsion is formed and the mixture is smooth, 45 seconds to 1 minute. If the mixture is too thick and doesn't spread easily, add a little more oil.
Whisk the butter, milk, and pepper together in a medium saucepan set over medium heat. Taste and add salt, if desired. Heat until sauce is warmed through. Serve over grilled chicken, pork, or rice.