Place in a boiling pot of salted water (about 2 tsp of salt for a large pot of water). Boil until softened. Remove from heat and carefully drain water when soft.
Add parsnips to a blender and add milk, butter, salt and pepper.
Blend until smooth. Serve immediately.
Notes
Make-ahead up to 3 days in advance and store in a tightly sealed container in the fridge. Warm in the microwave before serving.