Trim the fat into smaller pieces, removing any excess tissue. This will ensure a cleaner and more flavorful end product. (Optional: if previous frozen, defrost a bit, then grind to smaller pieces)
Select aromatic herbs that complement the richness of tallow. Classic options include rosemary, thyme, onion, garlic and bay leaves. Wash and dry the herbs thoroughly to remove any dirt or moisture.
Ensure your pressure cooker is clean and in good working condition. Some pressure cookers have a specific setting for rendering fat, which can be very useful.
Place the trimmed fat pieces and the selected herbs in the pressure cooker. The amount of fat you use will depend on the size of your pressure cooker and the desired quantity of infused tallow. I've added a 1/4 cup water, but there may be no need to add water, as the fat will release its own moisture during the rendering process.
Close the pressure cooker and set it to a low-medium heat for 2 to 3 hours. As the fat begins to melt, it will release its rich flavors and incorporate the aromatic essence of the herbs. Avoid high temperatures that could scorch the fat or herbs.
After several hours, the fat will have fully rendered and absorbed the flavors of the herbs. Carefully open the pressure cooker and let the mixture cool. First strain through gravy separator, and also remove any excess water and keep only the tallow. Then strain the liquid tallow through a few layers of cheesecloth or 350 fine mesh strainer into glass jars. This will remove any solid residue, leaving you with a beautifully clear and aromatic herb-infused tallow.
Seal the glass jars and store the infused tallow in refrigerator. It will solidify as it cools. Optionally store the tallow upside down so that any moisture will solidify on the top when you open to jar. The infused tallow can be used in a variety of dishes, such as roasted vegetables, seared meats, and even baked goods. Its high smoke point makes it ideal for high-heat cooking methods.