Heat the butter in a heavy-bottomed saucepot.
Add the onion and cook a few minutes until the onions are soft but not brown. Add the cauliflower and stock.
Simmer for 15 minutes or until the cauliflower is soft. Remove from the heat and let cool.
Purée in a blender until smooth.
While the bisque is cooling, make the brown butter and sear the scallops. Place the stick of butter in a large saucepot and cook until the butter foams and starts to brown for about 5 minutes.
Pour the browned butter into a glass or metal bowl to cool.
Sear the scallop by heating a small sauté pan over high heat. Add the oil and heat until smoking hot.
Season the scallops with salt and pepper and sear for 2 minutes or until golden brown. Turn the scallop over to sear the other side for another 2 minutes or until cooked through.
To serve, heat the bisque and divide it into soup bowls. Place a scallop in each bowl and drizzle bisque with a teaspoon of brown butter.