The components of premium ice cream are exactly those necessary to make light cakes, custard pies, and bread pudding: eggs, sugar, cream. In fact, melted ice cream yields super-light and fluffy baked goods—which is surprising, given all the cream.
You must use full-fat premium ice cream. It has much less air whipped in, so it will melt to about the same volume as the container.
And believe it or not, what looks like a pint isn’t always a pint. Some premium ice creams are now sold in pint-like containers while they in fact contain less (say, 14 ounces rather than 16). If the “pint” you have is indeed less than a pint, pour the melted ice cream into a liquid measuring container, then add enough whole milk, half-and-half, or heavy cream to bring the measure up to 1 pint (or 2 cups).
When the recipe says “melted,” we mean it. Set the pint out on the counter for a good while—or leave it in the fridge overnight, then set it out on the counter while you gather the other ingredients and heat the oven. Microwaving the frozen ice cream won’t work. You’ll end up with spots that are too warm, which can then curdle the eggs right in the batter.
Unfortunately, these recipes will not work with coconut-, soy-, or nut-milk ice creams. They often have too many other stabilizers and thickeners to work here.