Preheat oven to 350 degrees F.
In a large bowl mix the vinegar, soy sauce, and sesame oil together and pour over the tenderloin, turning every 10 minutes, for 30 minutes. Pat dry. Season with salt and pepper.
Heat 2 tablespoons of olive oil in a medium saute pan over high heat. Sear the tenderloin until evenly colored and transfer to the oven. Cook until the pork reaches the internal temperature of 145 degrees F. Remove from the pan and allow to rest 15 minutes. Thinly slice.
While tenderloin is in the marinade, in a small pot over high heat add the remaining 2 tablespoons olive oil and saute the onions, fennel, garlic and thyme until just colored. Reduce the heat to low and deglaze with the sake. Cover with a lid and cook for 30 minutes, stirring periodically until the onions are translucent and soft. Remove from heat.
In a small bowl, using a fork, mix in the remaining herbs and the goat cheese and season with and salt and pepper, to taste.
While the onions are cooking, thinly slice the bread. Rub each piece with a garlic clove and season lightly with salt and pepper. Drizzle each piece with olive oil and bake until golden but still soft in the center, 10 minutes.
On a piece of garlic crostini spread a thin later of goat cheese mixture. Top with a thin slice of tenderloin, then the onion mixture and lastly dollop of creme fraiche.
Recipe courtesy of Nathan Lyon