I haven't worked out the cost comparison yet, but on the basis of taste, the homemade Irish cream wins hands down, in my opinion. The flavors of the Irish whiskey, chocolate, and coffee (yes, I used instant coffee -- how else am I going to get it out of my cupboard?) really came through. The commercial mixes (Bailey's, Carollan's, etc.), by comparison, have no notable flavor standouts - just chocolate milk with a cloying sweetness and mild alcoholic effect. (Which is not to say I would turn a glass of it down if it presented itself in my life!)
I followed the "top secret" website's recipe, using, as some posters recommended here and there, sweetened condensed milk in place of evaporated milk + granulated sugar. Making it yourself, you can tweak it as needed - if the sweetened condensed milk effect is too syrupy, cut with skim or lowfat milk; if more alcoholic ping! is needed, add some Irish whiskey and then tweak with any of the other ingredients. Of course, you can also buy a bottle of commercial Irish cream mix and tweak it, but as I said, I haven't done the math on that yet.
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