Kabocha Squash and Potato Croquettes with Snowy Cabbage

Name: Kabocha Squash and Potato Croquettes with Snowy Cabbage
Ingredients: 1 small head green cabbage; 4 radishes; 1/2 kabocha squash, about 1 lb. (500 g), halved and seeded; 2 Tbs. vegetable oil, plus more for brushing and frying; 3 lb. (1.5 kg) russet potatoes; 3 yellow onions, diced; Kosher salt; 2 cups (10 oz./310 g) all-purpose flour; 5 eggs, beaten; 3 1/2 cups (8 oz./250 g) panko (Japanese bread crumbs); 1 Tbs. sugar; 1 Tbs. Japanese curry powder, preferably S&B; Lemon wedges for serving; Tonkatsu sauce for serving