Cook white beans according to packet directions.
Heat the oil and half the butter in a large saucepan over medium heat. Cook the leek and garlic for 4 minutes until soft.
Stir in the cauliflower and white beans. Add milk and stock. Cover and bring to the boil. Reduce heat to low. Simmer, stirring occasionally, for 15 minutes or until tender.
Drain, reserving 2 tbs of cooking liquid.
Return the cauliflower bean mix and reserved cooking liquid to the pan. Season with McKenzie's Salt & Pepper Grinder. Blend with a stick blender until smooth.
Heat a small frying pan over medium heat. Cook remaining butter for 2-3 minutes or until golden. Stir in the lemon juice and thyme and spoon sauce over mash.