Heat the broiler to high.
Heat olive oil in a large skillet over medium heat.
Add the onion and cook for 5–6 minutes until softened.
Stir in the garlic and red pepper flakes. Cook for 1 minute until fragrant.
Pour in the vegetable broth and white grape juice mixture. Simmer for about 1 minute until slightly reduced.
Add the chickpeas with their liquid and cook for about 3 minutes.
Stir in the kale along with the salt and pepper. Cook for 3–4 minutes until wilted.
Remove from the heat and fold in the chopped basil.
Place the sourdough slices on a baking sheet and broil for about 1 minute per side until golden.
Rub each slice with the cut side of the lemon.
Spoon the Kale and Chickpea Toasts mixture generously over the toasted bread.
Finish with grated Parmesan and a drizzle of olive oil before serving.