Line a large baking tray with baking paper. Place sweet potato on prepared tray, drizzle with 1 tablespoon olive oil and toss to coat. Bake in a 200 °C preheated oven for 30 minutes or until tender. Cool slightly. Transfer to a large bowl. Mash well.
Add salmon, shallots, egg and ¾ cup breadcrumbs to sweet potato. Season with pepper. Mix until well combined.
Place remaining breadcrumbs on a large plate. Divide salmon mixture into 12 even portions. Shape portions into 7 cm round patties and toss in breadcrumbs to lightly coat.
Heat remaining oil in a large non-stick frying pan over a medium-high heat. Cook patties in 2 batches for about 3 minutes on each side or until golden brown. Transfer to a baking paper-lined baking tray.
Meanwhile, to make dressing, whisk all ingredients in a small bowl with 1 tablespoon water until combined. Season with pepper.
Serve salmon cakes with salad, dressing and lemon wedges.