Crumble the feta cheese block into a food processor then add sour cream and mayonnaise. Process until feta cheese is completely velvety and no longer gritty, 3-4 minutes, scraping down the sides 2-3 times.
Scoop feta mixture into a mixing bowl then add green onions, dried dill, and pepper, and then stir to combine. Cover then chill for at least 12 hours before serving. Will keep in the fridge for 4-5 days.
