Combine the butternut, water, milk, and garlic and chilli powder ( if using )in a saucepan over medium-high heat. Bring to a boil, reduce heat to medium and until the butternut is tender. This should take about 15 minutes. Allow to cool before pouring into a blender with some milk or cream and blend until smooth.
Pour into a pot and add grated cheese and dried chilli flakes ( if using) Set aside
Boil the pasta according to the package instructions. Cook the pasta just until al dente, the pasta should not be too soft, it should be cooked but be still a little firm.
When the macaroni has just 5 minutes left to cook, toss in the chopped kale ( if using)
Strain out the water from the macaroni and kale and fold into the prepared butternut sauce. Top with garlic croutons and parmesan if you prefer.