Makes1 THICK 13- BY 9-INCH "PIZZA"
                    
                
                
                    
                        
                            - Active time:1 HR
 
                        
                            - Start to finish:2 hr (INCLUDES MAKING DOUGH AND RISING)
 
                        
                    
                
             
            
                
                    
                    Richard Bertinet, The Bertinet Kitchen, Bath, England 
                
            
            
                
                
                
    
      
          
          
          
              
              
              
          
          
          
          
          
              
              
              October 2009
            
          
          
      
  
                
                
            
            
            
                
            
            
            
            
            
                
                    
                    
                    
                        
                            
                            
                            
                                
                                    
                                        - 
                                            
                                            
                                            Fougasse dough, risen for 1 hour
                                            
                                        
 
                                    
                                        - 
                                            3
                                            tablespoons
                                            unsalted butter, divided
                                            
                                        
 
                                    
                                        - 
                                            1
                                            
                                            onion, halved and thinly sliced lengthwise (1½ cups)
                                            
                                        
 
                                    
                                        - 
                                            1
                                            cup
                                            large leek (white and pale green parts only), halved lengthwise and thinly sliced crosswise, then washed  (1 ½ cups)
                                            
                                        
 
                                    
                                        - 
                                            4
                                            
                                            large egg yolks
                                            
                                        
 
                                    
                                        - 
                                            8
                                            oz
                                            crème fraîche (1 cup)
                                            
                                        
 
                                    
                                        - 
                                            1/2
                                            teaspoon
                                            grated nutmeg
                                            
                                        
 
                                    
                                        - 
                                            1
                                            cup
                                            coarsely grated Gruyère (3 oz)
                                            
                                        
 
                                    
                                
                            
                         
                    
                 
            
            
            
            
            
                
            
            
            
            
                
                    
                    
                    
                        
                            
                                
                                
                                
                                    
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Preheat oven to 425°F or convection oven to 375°F with rack in middle position.
                                         
                                    
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Scrape risen dough, without deflating, onto a well floured work surface and dust top with flour. Let stand 5 minutes. Transfer dough, knocking off excess flour, to a lightly greased baking pan and press into bottom and up sides with fingers.
                                         
                                    
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Melt 2 tablespoons butter in a medium heavy skillet over medium-low, then add onion and leek and cook, stirring, until softened, about 5 minutes. 
                                         
                                    
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Whisk together egg yolks, crème fraîche, nutmeg, and 1/2 tsp each of salt and pepper in a large bowl, then stir in leek mixture.
                                         
                                    
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Pour mixture onto dough, spreading vegetables evenly, then sprinkle with grated cheese. 
                                         
                                    
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Bake until crust is browned and filling is puffed and golden, about 20 minutes (12 to 15 minutes in convection oven).
                                         
                                    
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Transfer pan to a rack to cool slightly then remove from pan and cut into serving pieces.
                                         
                                    
                                
                             
                        
                    
                    Cooks' Note:  You can use a 15- by 10-inch 4-sided sheet pan for this recipe, but the crust will be thinner.