Whisk together milk, eggs, vanilla, cinnamon and powdered sugar. Dip whole croissants into egg mixture and let sit 1 min, flipping over after 30 sec (you can cut the croissants; however, they will absorb the custard very quickly, so if cutting, dip and remove immediately).
Meanwhile, whip cream to stiff peaks, then fold into the ricotta, adding a pinch of powdered sugar, if desired.
Warm a large skillet or griddle over medium-high heat and add a tablespoon of butter when hot. Immediately add a few croissants but don’t crowd; gently press to flatten slightly. Flip after two min, then cook 2 min more until heated through.
Transfer to serving plates. Layer croissants with whipped cream and ricotta mixture and raspberries. Drizzle with maple syrup, as desired. Serve immediately.