Make pickled red onions and chipotle sauce. Chill and reserve.
Using a 3-inch round biscuit cutter, punch out circles of lettuce about 3 or 4-inches in diameter. Chill until needed.
Slice radishes into thin round circles. Chill until needed.
To assemble, reheat the sausage in the microwave, if needed. Place a spoonful of sausage in a lettuce cup. Top with a few pickled onions, sliced radishes, a dab of chipotle crema and a cilantro leaf.
Slice the red onions and place in a large glass bowl. In a saucepan, bring the sugar, rice wine vinegar, white vinegar, and water to a boil, stirring until the sugar is dissolved. Pour the brine over the sliced onions and let sit until the liquid comes to room temperature before chilling. Store the mixture in an airtight container in the refrigerator until needed. The pickled onions will keep for at least 3 weeks.
Mix just the adobo sauce from the canned chipotle peppers into the crema to the desired spiciness.
Iceberg lettuce will form a natural cup shape because of the curve of the leaf.