1. Add beans to a large pot and cover with water. Add yellow onion, four garlic cloves, the bay leaf, and thyme sprigs, then season very generously with salt. Bring to a boil; use a slotted spoon to skim off any foam that rises to the top. Reduce heat to medium-low and simmer gently until beans are tender, 1 to 1 1/2 hours (they should be soft but still have some structure); drain, discard onion and bay leaf, and set aside.
2. Meanwhile, mince remaining garlic cloves. Combine 2 tablespoons oil and 1/2 teaspoon minced garlic in a small saucepan and cook over medium heat until garlic is soft and fragrant. Let cool 5 minutes, then stir in sage and let cool completely. Transfer to a small bowl and stir in lemon zest and a pinch each of salt and red pepper flakes (if using) to make the gremolata; set aside.
3. When beans are cooked, melt 2 tablespoons butter in a large, heavy-bottomed pot over medium heat. Add sweet onions, season with salt, and cover. Cook, stirring frequently, until softened, about 15 minutes. Add remaining minced garlic, cover, and cook 5 more minutes. Add beans and stock and bring to simmer, then cook, stirring occasionally, 5 minutes; remove from heat.
4. Working in batches, puree beans and stock in a blender or food processor and season with salt and pepper to taste; transfer to a large bowl. (Feel free to leave some stock behind; you can always add a bit more to adjust the thickness before serving) Rinse out pot, then return soup and cover to keep warm.
5. Slice mushrooms into small pieces. Melt 2 tablespoons butter in a large skillet over medium-high heat. Add one-third of mushrooms (or enough to form one roomy layer) and season with salt. Cook, flipping once, until mushrooms are golden brown on both sides, 6 to 8 minutes. Transfer to a large plate and repeat with remaining mushrooms and butter, seasoning with salt as you go.
6. When ready to serve, bring soup to a gentle simmer over medium-low heat and season with salt and pepper to taste, adding a bit more water or stock as needed to loosen. Divide soup among bowls and top with a spoonful of mushrooms, then sprinkle gremolata over top and drizzle with a bit of olive oil.
Source: Hannaford fresh Magazine, October - November 2020