Reduce heat to low and add remaining 1 teaspoon oil. Add reserved chopped scallion mixture and remaining 1 1/2 teaspoons curry powder; cook, stirring, until fragrant, about 2 minutes. Add peas and broth, increase heat to medium-high and bring to a simmer. Cook until peas are heated through, about 3 minutes. Add shrimp and cook about 1 minute more. Season with salt and pepper. Garnish with reserved sliced scallion and serve.