Melt the butter in a large sauce pan over medium heat. Cook the celery and onion in the butter, stirring frequently, for 5 minutes. Add the garlic and cook another 2 minutes. Stir in the flour, curry powder, and red pepper; cook and stir 1 minutes. Pour in the chicken broth and bring to a boil. Reduce heat to low and simmer 20 minutes, stirring frequently. Mix in the coconut milk and peanut butter; continue to heat while stirring until completely heated through. Remove from heat.