Stud the onion with the cloves and place it in a saucepan. Add the bay leaf and pour in the milk. Heat gently until just below simmering, then remove from heat and let it infuse for at least 15 minutes
Remove the crusts from the bread and tear into small pieces
Remove the onion and bay leaf from the milk. Stir in the torn bread and let it soak for about 10 minutes until it softens
Stir well, then mash with a fork or whisk to achieve a thick, creamy consistency
Stir in the butter, season with salt, white pepper, and a pinch of nutmeg if using