To make the vinaigrette: Whisk together the shallot, lemon juice, mustard and 1 teaspoon honey in a small bowl; season with salt and pepper. While whisking, slowly drizzle in the olive oil and whisk until emulsified. Add salt and pepper to taste.
Heat 1/4 cup canola oil in a small saucepan over medium-high heat until it shimmers. Add capers and cook until opened and crisp, about 30 seconds. Use a slotted spoon to transfer to a plate lined with paper towels. Set aside.
To prepare the farro: Put farro in a pot with 2 cups cold water, 1 teaspoon salt and 1/4 teaspoon pepper. Bring to boil over high heat. Reduce heat to low, cover and cook until farro is tender and all liquid has been absorbed, about 40 minutes. Transfer farro to large bowl and add 2 tablespoons vinaigrette; toss to coat.
To prepare the salmon: Preheat oven to 250 degrees. Lightly oil a 9- by 13-inch baking dish.
Heat 1 tablespoon canola oil in large skillet over medium-high heat until it begins to shimmer. Add garlic and cook, stirring, until fragrant, about 30 seconds. Add mustard greens and cook, tossing, until slightly wilted, about 1 minute. Add 1/4 cup water; season with salt and pepper. Cook, tossing, until greens are completely wilted, about 3 minutes. Stir in remaining 1 teaspoon honey. Transfer to bowl with farro and stir to combine. Transfer the mixture to the prepared baking dish and set aside.
