Portobello + Artichoke + Walnut Pesto Panini

• 4 tbs olive oil, divided, plus extra for brushing
• 1 lg red onion, thinly sliced
• sea salt
• black pepper
• 4 portobello mushrooms, stemmed and cut into 1/4″ slices
• artichoke walnut pesto
• 4 ciabatta rolls, cut in half
• 1 lg tomato, sliced
• 1/2 cup spinach or arugula

Directions:

1. Make or defrost the artichoke walnut pesto.
2. In a skillet, heat 2 tbs oil over medium heat. Add onions and let cook 20-30 minutes, until tender and carmelized. Season with salt, and transfer to a bowl.
3. When the onions have 15 minutes to go, heat remaining 2 tbs oil in a separate skillet. Saute mushrooms over medium-high heat. Season with salt and pepper to taste and cook until lightly browned and the juices have evaporated.
4. Heat a panini press on medium heat.
5. Assemble: Spread the artichoke walnut pesto on each slice of bread and layer onions, mushrooms, tomatoes, and spinach / arugula in between the slices.
6. Cook on the panini press for a minute or two (be careful not to over-toast the bread as ciabatta rolls can become hard).
7. Slice panini in half diagonally and serve immediately.