Easy , Awesome Artichoke Filling for Panini or Focaccia

This is an adopted recipe that looks wonderful, but I haven't actually tried it myself. The OP had this to say: "What could be more yummy for a luncheon or casual dinner than a grilled Panini sandwich? Super elegant and tasty artichoke filling gives this sandwich great flavor and color! My family and friends rave every time we make these. I invite everyone over and we have a Panini Grilling party, make your own...kids get in on the act too and love it!"

• Ready In: 40 mins
• Yields: 4 sandwiches

Ingredients

• 5  tablespoons extra virgin olive oil
• 1  onion, finely sliced
• 1 (10 ounce) package frozen artichoke hearts, thawed, drained and sliced
• 1  teaspoon sea salt (to taste)
• 3 -5  drops  balsamic vinegar

Directions

1. Warm 2 tablespoons olive oil in a heavy skillet, over very low heat and cook onion for 30 minutes, or until soft, translucent and almost melting.
2. Stir in sliced artichoke hearts and cool over low heat for 3-5 minutes more.
3. Add salt (to taste, if needed) and let cool slightly.
4. Puree the mixture in blender or food processor.
5. Add just enough balsamic vinegar to bring out the taste of the artichokes and process briefly to mix well.