In a large Dutch oven, heat the butter and oil over medium heat.
Add in the onions and cook, covered, for 10 min, or possibly till soft.
2.
Remove the cover and continue cooking till brown and caramelized.
Add in the garlic and cook for one minute.
3.
Add in the collard greens, stock, salt, and red pepper flakes, cover, and cook over medium-high heat, stirring occasionally, for 30 min or possibly till tender.