Learn from my mistake and proceed as follows: use a good knife or a food processor to blitz your radishes into bits. Then stir in the remaining ingredients by hand. Adding everything to the food processor and pulsing again left me with watery radish mush instead of tiny radish crunches suspended in creamy, salty, herby radish butter. We spread ours on homemade bread.
Radish Butter with Oregano and Dill: Finely dice a small bunch of radishes, either by hand or in a food processor. Stir into 4 oz. softened salted butter along with a small handful each of oregano (or marjoram if you have it), dill, and snipped chives. Season well with black pepper and taste for salt before serving.