Cook the sweet potatoes: Peel and cube. Steam or boil until very soft, about 12–15 minutes.
Drain well.
Puree until smooth: Blend the sweet potatoes with 1/2 cup milk until silky. Add more milk, a splash at a time, to create a thick, pourable puree.
Boil the pasta: Cook macaroni in salted water until just tender. For toddlers, cook 1 extra minute for a softer bite.
Drain and set aside.
Make a quick roux: In a large saucepan, melt 2 tablespoons butter over medium heat. Whisk in 2 tablespoons flour and cook 1 minute to remove the raw taste.
Build the sauce: Slowly whisk in 1 to 1 1/4 cups milk until smooth and slightly thickened, 2–3 minutes.
Flavor it gently: Stir in 1/2 teaspoon garlic powder, 1/2 teaspoon onion powder, a small pinch of salt, and a pinch of paprika if using.
Add the sweet potato: Whisk the puree into the sauce until fully blended and creamy.
Melt in the cheese: Reduce heat to low. Stir in 1 to 1 1/2 cups shredded cheese by the handful until melted and smooth.
Optional yogurt boost: Off the heat, stir in 2–3 tablespoons plain Greek yogurt for extra creaminess.
Taste and adjust seasoning lightly.
Combine: Fold the cooked pasta into the sauce. If too thick, splash in a little milk to loosen.
Serve warm: For very young toddlers, cool slightly and cut pasta if needed. Garnish with a tiny sprinkle of cheese on top to entice.