Preheat an oven to 400 degrees F (200 degrees C).

Spoon 3 tablespoons olive oil over the cut sides of the garlic head; wrap tightly in aluminum foil.

Roast in the preheated oven until the garlic is soft, about 30 minutes; set aside until cool enough to handle.

Squeeze the roasted garlic cloves into a saucepan; pour the chicken stock into the saucepan and use a fork to mash the garlic into the stock. Cook the stock over high heat until the liquid is reduced in volume by half, about 10 minutes. Stir the cream into the stock and remove from heat; set aside.

Melt the butter with 1 tablespoon olive oil in a large skillet over medium-high heat. Season the scallops with salt and pepper; sear in the hot butter and oil mixture until opaque, about 3 minutes per side. Remove from heat immediately.

Stir the lemon juice into the cream sauce; spoon immediately onto 2 plates. Arrange the scallops on the plates. Garnish with the parsley to serve.