In a large, deep skillet, melt the butter in the remaining 2 tablespoons of olive oil. Add the carrots, celery, onion, leek and bay leaf. Cover and cook over low heat, stirring occasionally, until the vegetables have softened, about 10 minutes. Stir in the flour, then gradually whisk in the broth until smooth. Simmer over low heat, stirring often, until no floury taste remains, about 5 minutes. Stir in the cream and simmer until thickened, about 8 minutes. Stir in the peas, thyme and chicken and season with salt, pepper and a pinch of smoked paprika. Simmer for 5 minutes.