Slowly add the olive oil and whisk constantly until thoroughly mixed.

Bring slowly to the boil, whisking constantly, and cook for two minutes.

Return pan to medium heat, and whisk constantly until simmering.

Add the olive oil in a slow stream while whisking constantly.

Raise the heat and bring to a simmer, whisking constantly.

Whisk constantly until the mixture is very thick and warm, about 10 minutes.

Whisk constantly and very slowly add the hot cream mixture.

Continue adding cubes, one or two at a time, whisking constantly.

Whisk in the flour, and cook over low heat for 5 minutes, whisking constantly.

Add the butter quickly, one tablespoon at a time, whisking constantly.