Pork Wellington with Green Pea Duxelles and Champagne Sauce

Pork Wellington

• 1 pork tenderloin (approx. 500 g)
• 1 ¼ tsp fine sea salt
• 4 pinches ground black pepper
• 80 g onions, quartered
• 20 g unsalted butter, plus 1 Tbsp
• 200 g frozen green peas, defrosted
• 20 g fresh parsley leaves
• 20 g water
• 320 g puff pastry (see tip)
• 2 Tbsp breadcrumbs
• 12 slices prosciutto
  ou streaky bacon, cured and smoked
• plain flour, for dusting
• 1 medium egg, beaten

Champagne Sauce

• 150 g whipping cream
• 80 g onions, quartered
• 10 g unsalted butter, diced
• 150 g Champagne
  ou white sparkling wine
• 150 g water
• 10 g cornflour
• 1 heaped tsp chicken stock paste, homemade
  ou 1 chicken stock cube (for 0.5 l)