Add the copped red onions to the pot and add a little more butter or oil if needed. Cook the onions until softened and translucent, about 5 minutes.
1 Red Onion
Add the chopped leek, carrot and celery for another 5 minutes.
1 Leek, 1 Carrot, 1 Celery Stalk
Add the tomato paste and let it caramelize.
1 tbsp. Tomato Paste
Pour in the Red Wine and bring to a boil. Try to scrape off the brown pieces at the bottom of your pot. Reduce the heat and let the Red Wine evaporate for about 5 minutes.
1 cup Dry Red Wine
Pour in the Beef Stock, add the Bay Leave, Paprika and Thyme twigs. Add the Beef Rouladen back to the pot.
2 cups Beef Stock, 1 tbsp. Paprika, 1 Bay Leave, 2 Fresh Thyme Twigs
You can cook the Rouladen, covered, on the stovetop on low for about 90 minutes or until fork tender, but for the most even cooking I recommend transferring the pot (make sure it's oven-safe) to the oven preheated to 325°F and cook it there for about 90 minutes or until fork tender. If the liquid evaporates too much and gets too thick, add more stock.
Once the Rouladen are fork tender, remove them from the pot and keep them warm.
You have two options for the gravy:1. You can use a blender and puree the veggies and mix them with liquid. That creates a thick flavorful gravy. If it gets too thick, add more beef stock. Season to taste with salt & pepper.2. Pour the liquid and vegetables through a strainer and reserve the liquid. Return the strained liquid back to the pot and bring to a simmer. Season to taste with salt & pepper. Optional: Thicken the gravy with a cornstarch slurry. This will create a fine gravy. You can add back the veggies if you want. 1 tbsp. Corn Starch
Carefully remove the toothpicks or cooking twine from the Rouladen and return them to the gravy and heat through.