Bring a medium pot with farro and plenty of water to cover to a boil over high heat. Boil for 25-30 minutes, or until farro is softened but still chewy (Prepare remaining ingredients while farro cooks). Place a colander (or strainer, depending on hole size) in the sink. Drain farro in a colander and run under cold water to stop cooking. Shake well to remove excess water and transfer to a large mixing bowl along with peas.

Trim ends off shallot, peel, and slice into thin rings. In a small mixing bowl, whisk together Champagne vinegar, sugar, 1 Tbsp. water, and a pinch of salt. Continue whisking until sugar dissolves. Add sliced shallot and mix gently. Set aside to let flavors marry, at least 10-15 minutes. Mix gently every few minutes to ensure complete coverage.

Thoroughly rinse produce and pat dry. Trim ends off watermelon radish, peel, and slice as thinly as possible. Stack slices and halve through the middle to make half-moons. Halve grape tomatoes. Core apple and cut into 1/4" slices.

Remove shallot from pickling liquid and set aside, leaving liquid in bowl. Whisk in 1 Tbsp. olive oil to make vinaigrette and add to the bowl with farro. Don't worry if the farro is still a little warm; it will absorb the flavor of the vinaigrette even better. Toss to combine.

Add radish, apple, and grape tomatoes to bowl with farro and toss to combine. Add arugula and toss gently once more - if the farro is too warm, the arugula may wilt. Taste and season with a pinch of salt and pepper, if necessary.

Place a serving of farro-arugula salad on a plate and garnish with pickled shallot and crumbled goat cheese.