Preheat your oven to 425°F.
Trim the Brussels sprouts by cutting off the ends and removing any damaged outer leaves.
Wash and dry the Brussels sprouts thoroughly.
Place the sprouts on a baking tray. Drizzle with olive oil and sprinkle with sea salt and black pepper.
Mix the Brussels sprouts so they are evenly coated in oil and seasoning.
Roast the Brussels sprouts in the oven for 25 minutes, or until they are golden and crispy.
While the sprouts roast, melt the butter in a frying pan over medium heat and add the chopped garlic and sage.
After 2 minutes, add the cream to the pan and reduce the heat to low. Simmer until the mixture thickens slightly.
Remove the sprouts from the oven and transfer them to a casserole dish. Pour the creamy garlic mixture over the top.
Sprinkle the grated cheese and breadcrumbs evenly over the sprouts.
Return the dish to the oven and bake for an additional 10 minutes until the top is golden and bubbly.
Let the dish cool a bit before serving.