How to Make It
In a medium saucepan, melt the butter over moderate heat. Add the farro and cook, stirring, until toasted, about 2 minutes. Gradually stir in the boiling water, ½ cup at a time, stirring in more as the water is almost absorbed but the farro is still soupy, 10 to 15 minutes total. Cover the saucepan and simmer over moderately low heat until the farro is al dente, about 15 minutes.
Meanwhile, in a small saucepan, cook the raspberries over moderately low heat until they just begin to break down, about 3 minutes. Stir in the honey.
Stir the yogurt and cinnamon into the farro and season with salt. (If a looser porridge is preferred, stir in more boiling water, a tablespoon at a time.) Spoon the porridge into bowls, top with the raspberry sauce and pistachios and serve.