Set electric pressure cooker to "sauté" setting. Add oil. Once oil is hot, add onions and garlic. Cook until onions are almost translucent, about 2 minutes. Stir often to cook onions evenly. Add shiitake mushrooms and salt. Stir to combine and cook for about 1 minutes until warmed.
Add 3 cups of vegetable broth and drained red lentils. Cover with lid and lock in place. Make sure the pressure valve is on. Select "high pressure" and set for 8 minutes cook time. When timer beeps, allow pressure to release naturally for 10 minutes. After 10 minutes, manually release any remaining pressure.
Add in remaining 1 cup of vegetable broth, miso paste, and kale. Stir until miso paste has dissolved. Ladle warm soup into serving bowls. Garnish with sliced green onions and chili oil, if desired.