Make the crêpes: Melt the butter in a 10-inch nonstick or stick-resistant skillet over low heat. Transfer 2 tablespoons of the butter to a ramekin, set aside the skillet (do not wipe it out) and combine the remaining 3 tablespoons butter, the milk, flour, eggs and salt in a blender. Blend until smooth, scraping down the sides. Strain through a sieve into a bowl, cover and set aside at room temperature for 30 minutes, to allow the gluten (protein) in the flour to rest and ensure that your crêpes are tender.
To make the crêpes*
Heat a skillet over medium-high heat until hot but not smoking. Reduce the heat to medium.
: Brush the pan very lightly with butter and heat it until a tiny bead of water, when added, skips across its surface. Pour 1/4 cup of batter into the pan. Immediately lift the pan and tilt it all around until you have covered the whole bottom of the pan with the batter. After 30-45 seconds, peek to see if the bottom of the crêpe is golden brown. When it is nicely browned, slide your spatula underneath. And, with no hesitation, quickly flip the whole crêpe over. Transfer the cooked crêpes to a rack, where they’ll cool off slightly. A crêpe’s pretty side is the first one you cooked so when you roll up a crêpe, keep the pretty side on the outside. When the crêpes have cooled, you can stack them. (No, they won’t stick to each other; that is a myth.)
Once they are cool, set aside 4 crêpes for this recipe and wrap and freeze the remaining crêpes for another use.
Make the filling: Peel the bananas, cut them in half lengthwise, and then in quarters crosswise. Combine the butter, sugar, cinnamon and lemon juice in a large skillet and cook over medium heat, stirring until melted. Add the bananas and cook, gently turning over 1 or 2 times, until the bananas are just golden at the edges, about 5 minutes. Remove the skillet from the heat and add the rum. Return the pan to the heat, bring to a simmer, stirring, and simmer until the sauce is the consistency of honey, turning the bananas often to coat them with the sauce.
Arrange 1 crêpe on each of the 4 plates, spoon one-fourth of the banana mixture down the middle of each and roll up the crêpe to enclose the filling. Turn the crêpe so the seam is on the bottom. Top each filled crêpe with a scoop of ice cream, a drizzle of the sauce, and a sprinkling of walnuts.
*Cook’s Notes: For Successful Crêpes:
The one key tool required is the right pan. I use a stick-resistant ceramic or enamel pan (my favorite ones are made by Chantal). A non-stick pan will also do the trick; just don’t over-heat it.
Transporting the batter from the bowl to the pan can be messy. I keep the mess to a minimum by setting the measuring cup on a plate placed right next to the stove, then pouring out the batter 1/4 cup at a time. All the drips from the measuring cup will go on the plate, not the counter.
After the crêpes have cooled, if you are not going to use them all right away (or if you have made a double batch, you smart person), wrap them in the amounts you will use them later on – stacks of 4, 6, or 8.
Wrap the stacks first in plastic, then in foil. Contrary to what I was taught in cooking school, crêpes can be stacked on top of each other. You don’t have to put a piece of parchment between each one.
Label the crêpes and pop them in the freezer for future entrees or desserts. Let the stacks defrost in the fridge. If the crêpes stick together (because the butter in the crêpes is cold) when you are ready to use them, remove the plastic wrap, wrap them in the foil and pop them in a 350°F oven for 5 minutes and they will come apart easily.