In a large skillet over medium heat, heat olive oil and butter until melted. Add onions and sauté for 10-15 minutes, stirring often, until they are lightly browned.
Stir in soy sauce, sugar, and salt. Continue cooking, stirring often, for another 15-20 minutes until the onions are deep golden brown and very soft.
Once the onions are caramelized, add garlic, thyme, parsley, and pepper. Continue cooking for 1 minute.
Pour in sherry and white wine to deglaze the pan, using a wooden spoon to scrape any browned bits from the bottom. Let it simmer for 2-3 minutes.
Add the uncooked pasta, broth, and 1 ½ cups of water. Stir well and bring to a boil. Once boiling, reduce heat to low and simmer for 10-15 minutes, until the pasta is al dente. If the pasta absorbs too much liquid, add another ½ cup water.
Stir in the cheese and remove from heat. Top with toasted breadcrumbs and grated Parmesan, then serve warm. Enjoy your delightful caramelized onion pasta!