First add oil to deep pan and heat it before then adding the diced squash to the pan.
Roast the squash until it starts to brown.
Add diced onion, sugar, and a pinch of salt. Reduce the heat and cover the pot.
Stew together until the onions are soft 5-10 minutes. Add the stock and bring to a boil.
Reduce head and simmer for 30 minutes.
Add the butter and puree the soup with an emersion blender. Season with salt and pepper.
Top each bowl with 1 Tablespoon of toasted nuts (pine nuts, pecans, walnuts) if desired.