How to Make It
Make the mayo: In a bowl, whisk together all 5 ingredients. Refrigerate until ready to use.
Make the sandwiches: In a large nonstick skillet over medium heat, melt 1 tablespoon of butter in 1 tablespoon of olive oil. When the butter has melted and the foam subsides, crack 3 to 4 eggs into the skillet (as many as the pan can accommodate without crowding). Reduce the heat to medium low and cook for 1 minute, then tilt the pan enough so that the butter and oil pool on one side. Using a spoon, baste the whites of the eggs with the butter mixture until the whites are set, 3 to 4 minutes. Season lightly with salt, then transfer to a plate. Repeat with the remaining butter, olive oil and eggs.
In a large bowl, toss together the cabbage, sesame oil, ginger and ¼ teaspoon of salt.
Pull out and discard enough bread from the interior of each bread half to leave a ¼- to ½-inch-thick shell. Spread some mayo on each bread shell. Arrange half of the cucumber, jalapeño, cilantro and mint over the bottom halves, then divide the mortadella, eggs, slaw and pickles among the sandwiches. Top with the remaining cucumber, jalapeño, herbs and a generous squiggle of Sriracha. Serve the sandwiches with any remaining slaw on the side.