Open-Faced Koji Pâté Sandwich with Olives and Caramelized Onions

Fresh koji, plant-based pate on ciabatta bread with roasted onions and olives on wooden table

Koji is a variety of molds – Aspergillus oryzae – that are used in fermentation and are safe to eat. It contains about fifty enzymes that break down starches in grains such as rice into sugars and makes these sugars available for yeasts to consume in the fermentation process. The use of koji dates to the 8th century, and it’s a vital ingredient in many traditional Japanese products such as pickles, sake, soy sauce and miso. If you’ve ever eaten any of these things, you’ve enjoyed the transformative process of koji.

The folks at Prime Roots have developed meat alternatives using koji, and the results are tasty and satisfying. BriarPatch carries their pâté products – Harvest and Black Truffle. Here’s a simple recipe using pâté that’s a great way to see what the Prime Roots version is all about. 


  • 8 slices crusty artisan bread 
  • 1 cup pitted green olives (we like Frescatrano or Castelventrano) 
  • 3 Tbsp olive oil, plus more for drizzling 
  • 1 bay leaf 
  • 2 large yellow onions, halved/sliced 
  • ¼ tsp sea salt 
  • 2 6 oz tubs Prime Roots Koji pâté  
  • Fresh thyme sprigs, for garnish 


Heat oil in a skillet over medium heat. Add onions and bay leaf and stir/cook for 5 minutes until starting to soften. Add salt, reduce heat to medium low and cook for 50-80 minutes or until onions are very soft, golden brown and caramelized. Stir every few minutes as you go. Timing will depend on your type of pan, size of onions and heat of your stove. 

If onions start to stick to the pan, reduce heat to low. To speed things up after 50 minutes, turn heat higher for more caramelization and stir continuously to prevent burning. Remove from heat and allow to cool slightly. Discard bay leaf.

Slice bread, drizzle with a generous amount of olive oil and lightly toast in the oven on a sheet pan lined with parchment paper.  

Remove bread from oven and spread each surface with pâté. Top each slice with caramelized onions, olives and thyme sprigs.