Slice just enough off the top of the head of garlic to expose the cloves. Drizzle with 1 teaspoon of the oil and wrap in tin foil.
Roast in the oven for 30 minutes, until the cloves have softened.
While the garlic is roasting, prepare the vegetables.
Slice the baby carrots in half lengthways. Cut the celery stalks into thirds, then into batons. Slice the cucumber in three lengthways, then into thirds and cut into strips.
Place the butter beans in a food processor along with the remaining 2 teaspoons of oil, the lemon juice and water. Squish the garlic out of its skins and add it to the food processor, but take care as it may still be hot.
Blend until smooth and season to taste. Pour into a bowl and sprinkle with the toasted pine nuts. Serve on a board or platter alongside the prepared vegetables.