In a large pot, melt the butter over medium heat. Add the onions and celery and cook, stirring often, until softened and translucent, about 10 minutes.
Add the flour and stir to coat the onions and celery. Slowly add the chicken stock while whisking. Bring the mixture to a boil, then reduce to a simmer for 20 minutes. Remove from heat and use an immersion blender to puree the mixture until smooth.
Return to a low heat and whisk in the peanut butter and cream until smooth. Season with lemon juice and salt and serve immediately garnished with chopped peanuts and hot sauce if desired.