Preheat oven to 400°F.

Slice the top off the head of garlic to expose the cloves. Drizzle with 1 tsp olive oil, wrap in foil, and roast for 30–40 minutes until soft and golden. Cool slightly, squeeze out the cloves, mash, and reserve.

Cook pasta in salted boiling water according to package instructions. Drain, reserving ½ cup of pasta water, and return to the pot.

In a skillet, heat remaining olive oil over medium heat. Add half the minced garlic and sauté for 1 minute. Add chopped Swiss chard and cook for 2–3 minutes until wilted. Stir in lemon zest and juice. Season with salt and pepper. Reserve.

Wipe the skillet. Melt butter (reserving 2 tbsp for topping) over medium heat. Add remaining garlic and cook for 1 minute. Stir in flour and cook until bubbling and golden.

Gradually whisk in milk. Bring to a boil, then reduce to medium-low and stir constantly for 8–10 minutes until thickened.

Stir in cream, mashed roasted garlic, dry mustard, paprika, nutmeg, and season with salt and pepper. Cook 3–5 minutes until thick and creamy.

Add cooked pasta, Swiss chard mixture, and Gruyère cheese. Stir until well combined. Add pasta water if needed to loosen.

Transfer to a greased baking dish.

Mix reserved melted butter with breadcrumbs, garlic powder, and chopped chives. Sprinkle over the mac and cheese.

Bake for 20–25 minutes until golden and bubbly. Let rest 5 minutes before serving.