Heat a large skillet over medium heat and melt the butter until it foams.
Add the diced onion and drained chickpeas to the skillet and cook, stirring frequently, until the butter begins to brown and the onion becomes translucent, about 5–7 minutes.
Stir in the minced garlic and paprika and cook, stirring constantly, for 1–2 minutes until fragrant.
Pour in the marinara sauce, bring the mixture to a gentle simmer, then reduce the heat and simmer uncovered for 8–10 minutes, until the sauce thickens slightly.
Reduce heat to the lowest setting and stir in the chopped spinach until wilted, about 1 minute. Remove from heat and season with salt and pepper to taste.
Heat 1/4 cup olive oil in a separate skillet over medium-high heat. Slice each sourdough piece in half widthwise and fry until golden and crisp on each side, using tongs to flip; transfer to paper towels and sprinkle with salt.
Serve the saucy chickpeas in bowls or spoon them over the toasted sourdough. Top with grated Parmesan and fresh basil or parsley if desired.
Optional couscous: bring 1 cup water to a boil in a small pot, remove from heat, stir in 1 cup couscous, cover and let sit 2–4 minutes, then fluff and season with salt and pepper; divide among bowls and top with saucy chickpeas.
