I start by combining vinegar, water, sugar, and salt in a medium saucepan. Then I add peppercorns, mustard seeds, and red pepper flakes if I want a spicy edge. Bringing it to a boil and then simmering for 5 minutes allows the flavors to meld perfectly.
While the liquid simmers, I layer peeled eggs, sausage slices, and thinly sliced onions in a clean glass jar. Careful layering ensures every bite gets a mix of flavors. Once the brine is ready, I pour it over the ingredients, making sure everything is fully submerged.
After the jar cools to room temperature, I seal it and place it in the fridge. I usually let it marinate for 2–3 days for the best flavor. The eggs and sausage soak up the brine and become beautifully tangy and savory.