In a casserole pan, heat the oil & melt the butter.
Add the leeks & garlic to the pan. Season them with salt & pepper. Cook for 5 minutes over medium to high heat, stirring occasionally.
Add the green beans, carrots, sweet corn, stock & rice to the pan. Bring to a boil & then let simmer for 20 minutes. Add the prawns to the pan & cook with the pan covered for 5 minutes, over low heat.