For the orzo
Salt the chicken very well on both sides.
Put a frying pan on high heat, pour half of the olive oil and sauté the chicken until it gets golden brown color on one side, flip it over and sauté this side for less time. Remove the chicken and place it on absorbent paper.
Heat a pot on medium heat, add the remaining olive oil and cook the onion until it starts to soften, for about 3-4 minutes. Add the orzo, increase the heat s little bit and continue sautéing until the orzo gives off a soft roasting aroma, for about 3 minutes. Then flavor with white wine and once it is completely evaporated add the broth and bring to boil. Salt, stir regularly and once almost all the liquids are absorbed, continue adding the broth gradually, stirring regularly and salting at times, being sure that all the liquids are absorbed before adding the next dose.
At the last dose of the broth, the orzo is cooked al dente and has obviously smoothened. Lower the heat a lot and add the chicken, the grilled mushrooms, the butter, the kefalotyri cheese, the fresh thyme and the fresh onion. Stir to integrate the butter and kefalotyriso that the orzo is smoothened properly. If the orzo is thicker than you want, you can add a little more broth or water to dilute it. Try and fix the taste according to your taste.
Use truffle oil to give the orzo a distinct aroma.