For the crêpes:
1 cup (4 1/4 ounces) all-purpose flour
2 large eggs
1 cup whole or 2% milk
1/4 cup water
1 tablespoon granulated sugar
1 teaspoon pure vanilla extract
1/4 teaspoon kosher salt
Unsalted butter for the pan

For the filling:
1/3 cup packed dark brown sugar
3 tablespoons unsalted butter
4 ripe bananas, peeled and sliced
1/4 teaspoon ground cinnamon
1/4 cup dark rum, such as Meyer's
1/2 teaspoon vanilla bean paste or pure vanilla extract
Vanilla ice cream, for serving (optional)