Preheat the oven to 200°C (400°F). Grease a baking dish with butter or cooking spray.

Peel and thinly slice the potatoes and onions. Set aside.

In a saucepan, heat the milk and vegetable stock until warm. Stir in the grated cheese until it melts and forms a smooth sauce. Season with salt and pepper.

In a separate pan, sauté the chopped tomatoes, bell pepper, and minced garlic until softened. Add chopped parsley and set aside.

Layer half of the sliced potatoes and onions in the prepared baking dish. Pour half of the cheese sauce over the potatoes.

Add the sautéed tomato and bell pepper mixture over the cheese sauce.

Layer the remaining potatoes and onions on top and pour the rest of the cheese sauce over the second layer.

Cover the baking dish with foil and bake in the preheated oven for 40 minutes.

Remove the foil and bake for an additional 10-15 minutes or until the top is golden brown and the potatoes are tender.

While the potato bake is in the oven, toss broccoli florets with olive oil, salt, and pepper. Roast in the oven for 20 minutes or until the edges are crispy.

Serve the cheesy sliced potato bake hot, with a side of roasted broccoli.