This is a bit fiddly, but you can make it a day ahead.
If you have fresh parsley, you can use 2 tablespoons of fresh, chopped, instead. Instead of marjoram you can use oregano. If you wish, instead of drizzling with the remaining 1/2 of the butter, you can use 4 tablespoons of olive oil. The mixture shouldn't need salt for most people's tastes, but if you wish you can add up to 1/4 teaspoon of salt.