Cook orzo a few minutes shy of package directions. Reserve the pasta water.

In a separate pan, I sautéed some mushrooms, but you could use literally any veg, tomatoes, onions, broccoli, artichokes, etc. Once browned, I stirred in the pesto and deglazed with a few tbsp of the reserved pasta water.

Mix in the drained orzo and add the feta cheese. Continue adding reserved pasta water until the desired consistency is reached. Finish with a good pad of butter and lemon juice, or fresh herbs, splash of cream, etc. This is just a baseline for the dish, really can do whatever you want with it.