Roast the garlic: Preheat the oven to 400 degrees F. Slice just the top off of the heads of garlic, to reveal their cloves. Lightly rub the garlic to loosen and remove any excess papery garlic skin. Wrap the garlic in foil, drizzling it with the olive oil before you seal the foil, then place in the oven and roast for 45 minutes – 1 hour, or until golden brown. Remove from the oven and set aside to cool.

1. Boil the sweet potatoes: Meanwhile, as the garlic roasts, cook the sweet potatoes. Place the diced sweet potatoes in a large, heavy-bottomed Dutch oven and cover with 6 cups cold water, or enough to completely submerge the sweet potatoes. Season with 2 tablespoons kosher salt. Place the pot over medium-high heat and bring to a boil. Reduce to a simmer and cover, cooking for 20 minutes, or until the sweet potatoes are fork-tender. Carefully strain and set aside.
2. Cook the bacon: Meanwhile, as the garlic roasts & the potatoes boil, prep the breadcrumb topping. Add the bacon to a large skillet over medium heat. Cook 5-6 minutes per side, until crisp & rendered. Leaving as much of the rendered bacon fat in the skillet as possible, transfer the crispy bacon to a plate or cutting board & set aside.
3. Prepare the bacon breadcrumb topping: Reduce the heat under the skillet used to cook the bacon to medium-low. Add the fresh herbs to the skillet, blooming them in the bacon renderings. Cook 1-2 minutes, stirring constantly, until fragrant. Add the garlic to the skillet & cook 30 seconds longer, stirring constantly, just until fragrant. Add the panko breadcrumbs to the skillet, cooking 4-5 minutes, while stirring constantly, until toasty & golden brown. Remove from the heat & transfer to a small mixing bowl. Finely chop or crumble the bacon, adding it to the breadcrumb mixture along with the grated parmesan. Season with ½ teaspoon kosher salt & ground black pepper as desired. Stir to combine. Taste & season with additional salt & ground black pepper as needed. Set aside.
4. Mash the sweet potatoes: For extra creamy mashed sweet potatoes, transfer the boiled sweet potatoes to a food processor & puree until smooth & creamy, working in batches, as needed, to avoid overcrowding the food processor. As you puree the sweet potatoes, mix in the roasted garlic – the cloves should squeeze out of the garlic bulb very easily. With the food processor running, slowly add in the butter, one tablespoon at a time, and the milk. Alternate as you go – a little butter, then a little milk. Taste and season with additional kosher salt & ground black pepper as desired – I add ½ teaspoon of salt, taste, & go from there. Once the sweet potatoes have reached your desired consistency, transfer to a bowl. Fold in the grated parmesan & whisked eggs. Set aside.
5. Assemble the savory sweet potato casserole: Reduce the oven temperature to 350 degrees F. Lightly coat a 9×13 baking dish with cooking spray. Transfer the roasted garlic sweet potatoes to the baking dish. Top with the prepared bacon breadcrumb mixture. Cover with foil.
6. Bake the savory sweet potato casserole: Transfer the savory sweet potato casserole to the oven. Bake 35-40 minutes, until slightly browned & warmed through. In the last 15 minutes of baking, remove the foil so the breadcrumb topping gets beautifully browned & crisp. 
7. Serve immediately. Enjoy!