bopNgrill Umami Burger Copycat Recipe!

My take on the bopNgrill's Umami burger. Saw this on Diners Drive Ins and Dives and man am I glad I decided to do this!
bopNgrill on FB: https://www.facebook.com/bopNgrill-24...
Ballistic Griddle: craycort cast iron grate
Togarashi Seasoning: https://www.amazon.com/gp/product/B00...
Bonito Flakes: https://www.amazon.com/gp/product/B00...
Duxelles Recipe:
1/8 cup pork fat
1/8 cup unsalted butter
1/2 large sweet onion sliced in 1/4" strips
1/4 cup fine minced garlic
24oz minced portabello mushrooms
2 tbs (healthy pinch) Dried bonito shavings
1 1/2 tsp anchovy dashi
Salt and pepper to taste
Truffle oil
Melt pork fat and butter in skillet. Add onion and cook until it starts to become somewhat translucent. Salt and pepper.
Add garlic and continue cooking until garlic gets that translucent look.
Add bonito flakes and dashi, still well.
Add mushrooms and stir into the mix.
Cook until most of the water from the mushrooms is gone and the mixture thickens.
Drizzle with truffle oil and stir.