Mix dry and make a well on the center.
Add liquids, eggs and 2/3 of the fat. Mix until a rough dough forms.
Transfer to a lightly floured surface and knead for 10-15 minutes, until you get a soft dough.
Transfer to a lightly oiled bowl and let rest for 1hr at room temperature or until double in size.
Knead the remaining shortening in, and let rise for another hour.
Punch the dough and form a ball. Let rest in the counter for 10 min to relax. Roll into a rectangular shape, about 17 x 15 inches.
Spread the caramelized onions paste evenly and add the arugula. Shape into a roll and cut into 10 rolls.
Arrange on a baking sheet with baking paper and bake in a preheated oven at 350°F for 20 -25 minutes, or until the rolls are lightly golden on top.
If desired, brush the top lightly with olive oil as soon as they get out of the oven. Let rest on the baking sheet for a few minutes before transferring to a cooling rack to cool completely (if you can really wait for that!!)