In a medium stockpot, melt 2 tablespoons butter over medium heat. Add onion and garlic; cook until softened, about 5 minutes. Add sweet potatoes, broth, ginger, and pepper. Reduce heat to medium-low; cover and simmer until potatoes are very soft, about 45 minutes.
Add peanut butter; using a hand blender, purée until smooth. Stir in cream and salt. Remove from heat; cover and keep warm.
In a small sauté pan, melt remaining 6 tablespoons butter over medium heat. Add peanuts and rosemary; cook, stirring frequently, until butter turns a medium-brown color and has a nutty aroma, about 8 minutes. Serve soup drizzled with browned butter mixture.
Notes
FREEZE IT: Follow recipe through step 2, omitting the heavy cream. When reheating, whisk in the cream after the soup is completely thawed and comes to a simmer. Make the peanut topping when ready to serve.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/sweet-potato-peanut-soup/