Debeard and scrub the mussels. Transfer to a bowl of ice until needed.
Prepare the Rice:
Combine the rice, one tablespoon butter, 2 cups water, and salt to a small pot. Bring to a boil and stir once. Reduce heat, cover, and simmer for 15 minutes. Turn off the heat and rest, covered, for 5-10 minutes before fluffing with a fork.
Start the Broth:
As the rice cooks, prepare the broth. In a wide pot heat the remaining 3 tablespoons butter over medium heat. Add the onion and cook for 5 minutes until it begins to soften.
Add the garlic, scallions, and red Fresno pepper and cook for 1-2 minutes, being careful not to burn the garlic. Season with salt and pepper.
Cook the Broth:
Pour the chicken stock into the pot and bring to a boil for 5 minutes. Add the lemon wedges and cook an additional minute.
Cook the Mussels:
Add the mussels to the pot and reduce heat to low. Cover and cook for 7-9 minutes. Check on the mussels and remove all the opened mussels and transfer them to a bowl. Cover and cook any unopened mussels for 2-3 minutes more. Check the mussels again, transfer the opened mussels to the bowl, and discard any unopened mussels at this point.
Bring the broth back to a boil and taste and season with salt and pepper. Cook for 2-3 minutes more.
Divide the rice between shallow bowls. Ladle the broth over each dish and serve with mussels on top. Garnish with a drizzle of chili oil. Enjoy!