1. Bring 3 3/4 L of water to a boil. Reduce heat to a simmer. Gradually sprinkle the contents of the beef gravy package into the water, whisking until smooth. Whisk in the rosemary-garlic seasoning. Season to taste with salt and pepper.
2. Place the potatoes in a stainless-steel mixing bowl. Drizzle 2 Tbsp of oil over the potatoes. Season to taste with salt and pepper and mix thoroughly. Spread out on a parchment-lined sheet pan in a single layer. Place in a heated 162°C [325°F] convection oven for 20 minutes, or until tender.
3. Place the oil in a heated rondeau, as needed. Once the oil begins to smoke, add the beef. Sear on all sides. Season to taste with salt and pepper. Remove the beef and pour off any excess oil. Add the carrots, celery, onions and garlic to the rondeau. Season to taste with salt and pepper. Sauté until the onions are translucent.
4. Add the beef and undrained tomatoes to the vegetable mixture. Bring to a boil and mix frequently. Add 3 3/4 L of prepared warm gravy. Bring to a boil. Simmer 10 minutes, or until the vegetables are tender. Portion while still hot.
5. Spread containers out on parchment-lined sheet pans. Scoop 567 g portions into containers. Cover loosely with film wrap. Immediately place the tray on a rack and refrigerate. Let cool completely. Store in a single layer.
Microwave: Cook on high power, or until warmed through.
Oven: Place on a metal sheet pan and bake in a 176°C [350°F] heated oven 30 minutes, or until cooked through.