Preheat oven to 375* F.
In a heavy bottom stock pot or enameled cast iron dutch oven, cook the onions in olive oil until soft and until they start to turn golden brown. Add the diced garlic and cook until fragrant, about a minute or so.
Add the cubed up squash, apple, and chicken stock to the pot, season generously with salt and pepper and give everything a good stir. Turn up the heat and bring to a boil, then reduce the heat to a simmer, cover with a lid, and cook until the apples and the squash are soft, about 20-30 minutes.
While the soup is simmering, prepare the croutons by tossing them in 5 tablespoons of olive oil to really get them coated, and spread onto a baking sheet. Sprinkle with salt, pepper, and your chopped up fresh sage.
Bake the croutons for about 10-12 mins, until slightly golden brown, take out of the oven, and push the cubes of bread really close together, and sprinkle with the grated asiago and pop back into the oven for an additional 5 mins until cheese melts slightly, then remove from heat and turn off oven. (if you don't push the bread pieces together a lot of the cheese will melt between them on the baking sheet and you won't get that goodness on your croutons!)
When the apples and squash are cooked and soft, transfer everything to a blender and blend to desired consistency - if you have an immersion blender this would be the perfect time to use it!
Transfer the soup back into your pot, season with salt and pepper again, add the nutmeg, and a pinch or two of cayenne for some spice. If you want to thin out the soup a bit, (I usually do) add 1/2 cup water and give everything a stir.
Serve soup into individual bowls and top with croutons, enjoy!