Prepare the Creamy Base : In a medium mixing bowl, combine the cottage cheese, Dijon mustard, fresh dill, lemon juice, sea salt, and a few cracks of black pepper. Stir until well-incorporated and set aside. This allows the flavors to meld while the eggs cook.
Gently Cook the Eggs : Place the 8 eggs in a single layer in the medium saucepan and cover with cold water by at least one inch. Bring the water to a rolling boil over medium-high heat, then immediately reduce the heat to maintain a gentle, consistent simmer. Cook for exactly 11 minutes for yolks that are firm yet tender.
Shock and Peel : Using a slotted spoon, immediately transfer the cooked eggs from the hot water into the prepared ice water bath. Let them chill for at least 5 minutes. This step halts the cooking process and makes the shells easier to remove. Once cool, carefully peel the eggs.
Chop and Combine : Roughly chop the peeled eggs and add them to the mixing bowl containing the creamy cottage cheese base. Gently fold everything together until the eggs are evenly coated. Avoid over-mixing to maintain some pleasant texture.
Assemble the Tartines : Toast the slices of whole-grain sourdough to your desired level of crispness. While the bread is warm, mash a quarter of the avocado onto each slice.
Final Plating : Generously spoon the prepared egg salad mixture over the mashed avocado on each toast. Finish with a light drizzle of extra virgin olive oil and an extra sprinkle of fresh dill, if desired, before serving immediately.