Add farro and water to the Instant Pot. Close the cover and set to high pressure. Cook for 7 minutes and turn off pot. Allow 10 minutes for natural release. Turn release valve to release remaining pressure, and open. Drain the farro, spread on a baking sheet, and place in refrigerator to cool completely.
While the farro is cooling, place the oil, vinegar, mustard, shallot, salt and pepper in a small jar. Attach a lid and shake until combined.
Toss the tomatoes, peaches, and basil in a bowl with 3 tablespoons of the dressing.
Combine the farro and salad mixture and remaining dressing in a serving bowl, then spoon the tomato/peach mixture on top. Sprinkle with feta cheese and serve.
OPTION: If you don't have an Instant Pot for the farro, bring 3 cups of water to boil in a saucepan over high heat. Add the farro, lower the heat, cover the pot, and simmer for about 25 minutes until the farro is tender. Drain and spread on a baking sheet.