Cut off the top of the garlic head to expose the cloves. Drizzle generously with olive oil and set on a foil-lined rimmed baking sheet. Roast at 350° until completely soft and browned, about 45 minutes.
While garlic is roasting, add diced potatoes to a large pot and cover with cold water. Bring to a boil over high heat, then reduce to a simmer. Cook until tender, about 20 minutes.
When potatoes are done, drain and transfer to a large mixing bowl. Use a potato masher or stand mixer paddle to mash potatoes.
When garlic is done, squeeze cloves out of the husk and mash well. Add to potatoes.
Add browned butter, cream, and parmesan to potatoes and whip until smooth and creamy. Season with salt & pepper to taste.
Melt butter over medium heat in a medium pot. Saute onion and garlic until onion is translucent. Add rosemary & thyme and cook for another minute until fragrant.
Reduce heat to low and whisk in flour. Cook until light brown, then whisk in wine, scraping any browned bits off the bottom of the pot.
Slowly whisk in broth a little at a time, stirring constantly to keep the gravy smooth.
Bring to a simmer and let thicken to your desired consistency.
(Optional) For completely smooth gravy, blend with an immersion blender.
For vegan-friendly gravy, substitute olive oil for the butter.