Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce.

Cut potatoes into ½-inch-thick wedges. Halve jalapeño lengthwise and remove ribs and seeds for less heat, then thinly slice into half-moons. Halve, peel, and thinly slice half the onion (whole onion for 4 servings). Zest and quarter lime (for 4, zest one lime; quarter both). Peel and mince or grate garlic.

Toss potatoes on a baking sheet with a large drizzle of oil, salt, and pepper. Roast on top rack until browned and tender, 20-25 minutes.

Meanwhile, in a small microwave-safe bowl, combine jalapeño, sliced onion, juice from half the lime, ¼ tsp sugar (½ tsp for 4 servings), and a pinch of salt. Microwave until bright pink, 30 seconds. Set aside to pickle, tossing occasionally.

In a separate small bowl, combine BBQ sauce, ketchup, stock concentrate, juice from one lime wedge (two wedges for 4), and ¼ cup water (½ cup for 4).

In a third small bowl, combine garlic, mayonnaise, juice from one lime wedge (two wedges for 4), a pinch of lime zest, and a pinch of salt and pepper.

Pat tofu dry with paper towels; slice crosswise into ¼-inch-thick planks. On a plate, combine cornstarch and Fry Seasoning. Press tofu into cornstarch mixture until evenly coated; season generously with salt and pepper.

Heat a large drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Add coated tofu and cook until golden brown, 3-4 minutes per side. (You may need to work in batches for 4 servings.)

Add BBQ sauce mixture to pan with tofu. Cook, stirring, until tofu is coated and sauce is thickened, 1-2 minutes.

Remove pan from heat; sprinkle pepper jack over tofu and cover pan. Set aside until ready to serve.

Halve ciabattas and toast until golden brown. TIP: For extra richness, brush cut sides with melted butter before toasting. Use a toaster oven, or toast ciabattas directly on oven rack.

Fill ciabattas with cheesy BBQ tofu (spoon any remaining sauce from pan over top) and as much pickled jalapeño and onion (draining first) as you like.

Divide tofu subs between plates. Serve with potato wedges and garlic-lime mayo for dipping.