Preheat oven to 400°F

In a skillet, add oil and onions and cook until caramelized; set aside

On a floured surface, roll out the dough to ⅛ inch thickness. Spread the garlic on the pastry, then add the onions and layer the prosciutto

Roll the puff pastry from the long end into a pinwheel. Dust with flour and wrap with film wrap. Place in fridge for 1 hour

Remove from the film wrap and slice ¼ inch thick. Place on a sheet pan with parchment paper and bake for 10-12 minutes or until brown

Garnish with fresh basil and serve at room temperature