Ingredients

• 3 tablespoons, unsalted butter
  
• 3 tablespoons, il Fustino Mission Extra Virgin Olive Oil
  
• 2 large, yellow onions - halved lenghtwise and thinly sliced
  
• 1 sprig, rosemary
  
• 1/4 cup, milk
  
• 1 medium, egg
  
• flour for dusting
  
• 3/4 pound, prepared puff pastry
  
• 1 1/2 ounces, Stilton cheese - crumbled
  
• 2 tablespoons, pine nuts - toasted
  
• il Fustino 25 year old balsamic vinegar
  

Method

1. In a large flat bottomed skillet over low heat, melt butter and oil
   
2. Add onions and rosemary
   
3. Cook, tossing occasionally until onions are limp and golden brown, 30 to 40 minutes
   
4. In a small bowl, shick together the milk and egg until smooth
   
5. Stir in the onions
   
6. Preheat oven to 400 degrees
   
7. Line an 11" X 17" baking sheet with parchment paper
   
8. On a lightly floured surface, unroll and cut prepared puff pastry sheet to size. Place on baking sheet.
   
9. Use a fork to spread onion mixture evenly over pastry (let excess egg mixture drip back into bowl) leaving a 1 inch boarder
   
10. Scatter cheese and pine nuts over onion mixture
    
11. Use a pastry brush to dab edges of tart with leftover egg mixture
    
12. Gently fold over edges of tart to form a lip and brush with more leftover egg mixture
    
13. Bake until pastry is puffed golden, 25 to 30 minutes
    
14. Serve sprinkled with rosemary needles and drizzeled with il Fustino 25 year old balsamic vinegar. Serve warm or at room temperature.