Whisk the sugar, cream, buttermilk, condensed milk, evaporated milk, vanilla and candied pecans in a large bowl.
Pour into a bag.
Prop a 1-gallon zip-top freezer bag open in a large container; pour in the buttermilk mixture. Press out the air and seal. Chill the bag until ready to make the ice cream.
Fill your container.
Put about 10 cups ice in the container, filling it about three-quarters of the way, then pour in the sea salt. Nestle the sealed bag of buttermilk mixture in the ice.
Tightly cover the container with the lid. Shake vigorously for about 15 minutes, or until the buttermilk mixture is thick. How long it takes depends on your shakin'!
Serve and eat.
For soft-serve, rinse the outside of the bag, snip a corner and pipe into bowls. For firmer ice cream, freeze 1 hour before scooping. Top with caramel bananas, if desired.
Melt the butter in a skillet over medium heat, then add the pecans, brown sugar, granulated sugar and salt. Cook, stirring, until the sugar is dissolved and the mixture is sticky, 6 to 8 minutes. Spread the nuts on a baking sheet to cool, then refrigerate at least 10 minutes before using.
Melt the butter in a large skillet over medium-high heat. Add the bananas, stirring to coat. Sprinkle in the brown sugar and salt and cook, stirring, until the bananas are tender and coated with the sauce, 2 to 4 minutes. Spoon warm over ice cream.