Preheat your oven to 200°C (fan 180°C). Bring a large pot of salted water to a rolling boil — you should see big, vigorous bubbles breaking the surface. Drop in the green beans and blanch for exactly 3 minutes. The beans will turn a bright, vivid green and smell fresh and grassy. Drain them immediately and plunge into a bowl of ice water to stop the cooking. This keeps them snappy, not limp.

While the beans cool, heat the olive oil in a large frying pan over medium heat. Add the diced onion and cook for 4–5 minutes, stirring occasionally. You'll know they're ready when they turn translucent and release a sweet, mellow aroma, with edges just beginning to brown. Add the minced garlic and stir for 30 seconds until fragrant — the smell will shift from sweet to savoury.

Pour in the chicken stock and bring it to a gentle simmer. You should see small bubbles forming around the edges of the pan. Stir in the double cream and cream cheese, whisking until the cream cheese melts completely and the sauce turns smooth and pale gold. The mixture should coat the back of a spoon without being too thick. Season with salt, pepper, and smoked paprika, then remove from heat.

Drain the blanched beans and pat them dry with a clean tea towel. Transfer them to your 9x13 inch baking dish in an even layer. Pour the creamy sauce over the top, using a spatula to ensure every bean gets coated. The sauce should pool slightly around the beans — this keeps them moist during baking.

Sprinkle the grated cheddar evenly over the casserole. In a small bowl, mix the crispy fried onions with the breadcrumbs, then scatter this mixture over the cheese. Press down gently with your fingertips so the topping adheres to the sauce below.

Bake for 20–25 minutes until the top is deep golden brown and the sauce is bubbling up around the edges. You'll hear a gentle sizzle when you pull the dish from the oven. Let it rest for 5 minutes — the sauce will thicken slightly, and the layers will settle. Serve hot.