Preheat your oven to 400°F (200°C). Place the head of garlic on a small piece of foil, drizzle the exposed cloves with 1 tablespoon of olive oil, and wrap it tightly in the foil.

Set the wrapped garlic on a baking sheet and roast for 30 to 35 minutes, until the cloves are very soft and lightly golden. When cool enough to handle, squeeze the roasted garlic cloves out of the skins into a small bowl and mash them with a fork.

While the garlic roasts, place the potato chunks in a large pot and cover with cold water by about 1 inch. Add 1 teaspoon of the fine sea salt to the water.

Bring the pot to a boil over medium-high heat, then reduce the heat to maintain a gentle boil. Cook the potatoes for 15 to 18 minutes, until they are very tender when pierced with a fork.

Drain the potatoes well and return them to the warm pot. Let them sit for 1 to 2 minutes so some of the excess moisture can evaporate.

Add 4 tablespoons of the unsalted butter to the potatoes along with the mashed roasted garlic. Mash the potatoes until mostly smooth.

Pour in the warmed whole milk and the sour cream. Continue mashing or use a hand mixer on low speed until the mashed potatoes are creamy and smooth, being careful not to overmix.

Season the mashed potatoes with 1/2 teaspoon of fine sea salt and 1/2 teaspoon of freshly ground black pepper, or to taste. Cover the pot to keep the potatoes warm while you prepare the sausage gravy.

In a large skillet over medium heat, add the remaining 1 tablespoon of olive oil and the remaining 2 tablespoons of unsalted butter. Once the butter has melted, add the ground pork sausage.

Cook the sausage, breaking it up with a wooden spoon, for 6 to 8 minutes until browned and cooked through. Add the finely diced yellow onion and the crushed red pepper flakes, if using, and cook for 3 to 4 minutes more, until the onion is soft.

Sprinkle the all-purpose flour evenly over the sausage mixture. Stir well to coat the sausage and onion in the flour, and cook for 1 to 2 minutes, stirring constantly, to remove the raw flour taste.

Slowly pour in the chicken broth while stirring, making sure to scrape up any browned bits from the bottom of the skillet. Stir until the mixture is mostly smooth.

Add the heavy cream, dried thyme, paprika, garlic powder, onion powder, 1/4 teaspoon of ground black pepper, and 3/4 teaspoon of fine sea salt. Stir to combine everything evenly.

Bring the gravy to a gentle simmer and cook for 5 to 7 minutes, stirring often, until it thickens to a spoon-coating consistency. Taste and adjust the seasoning with additional salt or pepper if needed.

To serve, spoon a generous portion of the creamy roasted garlic mashed potatoes onto each plate or into a shallow bowl, then ladle the hot savory sausage gravy over the top. Serve immediately while everything is warm.