Combine fennel, water, and salt and pepper to taste in a saucepot over medium-high heat.

Bring to a boil, reduce heat to a simmer, and cook until there is only ¼ cup liquid remaining.

Pour fennel mixture into a blender. While blender is running, slowly add oil and puree until a silk consistency. Adjust the seasoning, if necessary.

Pour onto a large serving platter and set aside.