Preheat the oven to 400°F (204°C). Leave the garlic cloves unpeeled and coat them lightly in oil. Place them on a parchment-lined baking sheet and roast until golden brown—about 10 minutes for smaller cloves, and 15-20 minutes for larger ones. Once cool, peel the skins, remove the hard nubs, and set aside.

Scrub the potatoes clean. In a large pot, add potatoes, bay leaves, and enough water to cover them. Season with a pinch of salt.

Bring to a boil over medium-high heat and cook until a knife can be inserted smoothly into the potatoes, about 30-40 minutes. Drain and, if desired, peel the potatoes using the cold water method described: make a circular slit, soak in cold water, and peel.

In a large bowl, mash the boiled potatoes with the roasted garlic, milk, and butter until you achieve your desired consistency. Season with salt to taste and set aside.

Optionally, remove the sausage meat from the casings and break it into small pieces. In a skillet over medium-high heat, cook the sausage until browned and cooked through. Remove from the pan and set aside, keeping the drippings in the pan.

In the same pan with the sausage drippings, add the sliced onion. Cook over medium-low heat until brown and soft, about 15 minutes.

Add the beef stock, dark beer, and soy sauce, and simmer for 5-10 minutes to blend the flavors. Scrape any crispy bits from the bottom of the pan for added flavor.

Mix the cornstarch and cold water in a small bowl to create a slurry. Pour this into the simmering gravy, stirring continuously until thickened. Stir in the maple syrup.

In serving bowls, layer the mashed potatoes at the bottom. Top with cooked sausage and generously ladle over the gravy.