In a medium bowl, whisk together 1 cup dashi broth, 1 1/2 tablespoons dark brown sugar, and 1 tablespoon dark soy sauce until well combined. Set aside.
Preheat 2 tablespoons canola oil and 1 teaspoon sesame oil in a large nonstick pan over medium high heat. Add the squash, cooking for a few minutes until slightly brown. Flip and cook on the other side. Once both sides are browned and seared, add the dashi mixture (from the first step). Reduce heat to medium low and simmer for 20 minutes, or until the squash is tender when pierced with a fork, flipping the squash pieces about halfway through. Towards the end, most of the dashi mixture will have been reduced and the remaining liquid will be syrupy. Shake the pan to coat all the squash pieces and transfer to a plate.
Sprinkle 1 teaspoon togarashi over the squash, and garnish with scallions for serving.