Instructions

1. Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
2. Toss the halved Brussels sprouts with olive oil, ½ teaspoon kosher salt, and black pepper. Spread them out evenly on the prepared baking sheet.
3. Roast the Brussels sprouts in the preheated oven for 20 minutes, shaking the pan halfway through, until they are golden brown and tender.
4. While the sprouts roast, melt the unsalted butter in a medium saucepan over medium heat.
5. Add the minced garlic and cook, stirring frequently, until fragrant, about 1 minute. Be careful not to brown the garlic.
6. Sprinkle the all-purpose flour over the butter and garlic, whisking constantly to form a smooth roux. Cook for 1-2 minutes to remove any raw flour taste.
7. Gradually whisk in the heavy cream, continuing to whisk until the sauce thickens, about 3-5 minutes.
8. Remove the sauce from heat and stir in the grated Parmesan cheese, fresh thyme, remaining ½ teaspoon kosher salt, and lemon zest if using. Adjust seasoning to taste.
9. Transfer the roasted Brussels sprouts to a serving dish and pour the creamy Parmesan sauce over them, gently tossing to coat evenly.
10. Serve warm as a luxurious side dish to roasted meats, poultry, or a hearty grain bowl.