In a large cast-iron Dutch oven, heat oil over medium-high heat. Reduce heat to medium, add bacon, and cook, stirring occasionally, until browned and crispy. Set aside bacon to drain on paper towels, leaving drippings in the pot.
Increase heat to high, and add potatoes, stirring to coat with drippings. Cook, stirring occasionally, until browned, about 5 minutes. Reduce heat to medium, and add onion, shallot, garlic, rosemary, salt, and pepper, and cook, stirring, until the onion is translucent, about 5 minutes.
Add thyme, Cajun seasoning, salt to taste, and stock, and stir to incorporate. Taste for seasoning. Bring to a boil over medium-high heat. Reduce heat to medium-low, cover, and simmer, stirring occasionally, until the potatoes are tender and have absorbed the stock, about 30 minutes.
Remove from the heat, and discard thyme. Add green onion, reserved bacon, and cheese, and stir to combine. Garnish with green onion, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/smothered-potatoes/