Ingredients

• 2 large russet potatoes - I like mine skins on but you can peel them if you want
  
• 1 large celery root - this you MUST peel
  
• ¹/₂ cup heavy cream
  
• 2 cups buttermilk (full fat is just better)
  
• 1 handful of thyme (I go out back with my scissors, grab a handful and snip)
  
• 2 large cloves garlic
  
• ¹/₂ cup shredded parmesan cheese
  
• 1 cup grated pecorino cheese
  
• 1 cup grated fontina
  
• salt and pepper
  
• butter for the pan