Heat the vegetable oil in a large pot or Dutch oven over medium-high heat until shimmering. Add the onions, scallions, and salt, and cook until the vegetables are softened and just beginning to brown, about 5 to 7 minutes.

Stir in the garlic, chile, thyme, and cayenne. Cook until fragrant, about 1 minute—keep the aromatics moving to prevent the garlic from scorching.

Add the vegetable broth and butternut squash. Bring to a boil, then reduce the heat to medium-low, cover, and simmer until the squash is tender when pierced with a fork, 10 to 12 minutes.

Stir in the Swiss chard and coconut milk. Continue to simmer uncovered until the greens have wilted and are completely tender, about 5 minutes.

Transfer approximately 1 cup of the stew's solids and a splash of the liquid to a blender. Puree until smooth, then stir the mixture back into the pot to thicken the broth. If using a standard blender, hold the lid down with a folded kitchen towel to prevent steam from forcing the lid off.

Stir in the bitters and season with additional salt to taste. Serve hot in deep bowls.