How to Make It
Season the steaks with salt and pepper on both sides. Distribute the mustard onto one side of each of the steaks; distribute the chopped onion, pickle and bacon over the mustard, setting aside any leftover filling. Roll the steaks and secure with cooking twine.
In a Dutch oven, heat the butter or ghee on medium-high heat for 1 minute, then add the rolled steaks. Sear until browned, turning every couple of minutes. Remove the steaks and set aside.
Add the carrot, celery, thyme and leftover filling to the Dutch oven and sauté on medium heat for about 5 minutes, until the vegetables start to soften. Return the steaks to the Dutch oven and add the wine and broths. Bring to a simmer, then cover and reduce heat to low. Simmer for 2 hours, turning the steaks over halfway through.
After 2 hours, remove the steaks and place them on a cutting board. Strain the sauce and discard the vegetables, returning the strained sauce to the Dutch oven. Stir in the tomato paste and reduce the sauce by half over medium-high heat, about 5 minutes. Slice the steaks, then pour the sauce over the meat and serve.