In a small bowl, combine the chestnut honey and yakitori sauce. If the honey is too thick to mix well, warm it slightly until it blends easily. Stir until smooth.

Coat the filet mignon thoroughly with the prepared honey and yakitori marinade from Step 1. Cover the marinated meat with cling film and let it rest at room temperature for 3 hours to absorb the flavors.

Heat the oil and butter together in a heavy-bottomed casserole dish over medium-high heat. Once the mixture is hot and foamy, add the marinated filet mignon from Step 2 and brown it on all sides for a golden crust. Remove the browned filet mignon and set it aside on a serving dish.

If there's not enough fat left in the casserole, add a little more if needed. Add the finely chopped onion and cook over medium heat until soft and translucent. Stir in the julienned lemon zest and mix well, followed by the julienned dried apricots. Sauté all together for 2-3 minutes to combine the flavors.

Add the vinegar along with another splash of chestnut honey and yakitori sauce to the onion, lemon, and apricot mixture. Stir to combine, then cover and simmer for a few minutes until the mixture thickens slightly. I like to taste and add a touch more honey for sweetness at this point if the sauce needs more balance.

Return the browned filet mignon from Step 3 to the casserole dish on top of the thickened sauce. Cover and let cook over low to medium heat for 7 minutes. Flip the filet mignon, cover again, and cook for another 7 minutes to ensure even cooking. Remove from the heat and let rest, covered loosely with aluminum foil.

Slice the rested filet mignon and serve it with the sauce spooned on top. Accompany with either potatoes cooked in the field or creamy mashed potatoes, as preferred. For extra freshness, I sometimes garnish with a bit of extra lemon zest.