Preheat oven to 350°F/180ºC.
In a medium skillet over medium high, melt butter. Add onions and season with salt; sauté for 2 minutes. Sauté until translucent, about 2 minutes.
Add garlic and sauté for 1 minute.
Transfer the mixture to a large bowl and allow to cool.
In a small bowl, combine glaze ingredients; set aside.
When onion mixture is cooled, add ground pork, beaten eggs, breadcrumbs, tomato paste, ketchup, Worcestershire sauce, warm milk, thyme leaves, rosemary, and ground mixed peppercorns; mix well. Transfer the mixture to a 9x5x3 loaf pan.
Spoon half glaze mixture over, and spread evenly to cover the top.
Transfer to the preheated oven and bake for 60 minutes.
About 20 to 15 minutes before the end of cooking, remove from the heat and apply the remaining glaze, spreading it out evenly.
Return to the oven and continue baking until done.
Remove from the heat and let it rest for 15 minutes before slicing. Sprinkle on fresh chopped parsley before serving.