Can I use evaporated milk instead of sweetened condensed milk?
No. Evaporated milk is unsweetened and much thinner, so the fudge will not set the same way. You need sweetened condensed milk for the texture and structure here.
Why is my fudge grainy or gritty?
The two biggest culprits are overheating and moisture getting into the chocolate. Too much heat can scorch the mixture or cause the chocolate to break, and even a tiny bit of water (a wet spatula, steam, or a splash from the sink) can make chocolate seize, which looks thick, dull, and gritty.
To prevent it, keep the heat low, use a dry spatula, and stir until it is just melted. If you already poured it and it tastes gritty, you can sometimes rescue it by gently remelting the batch over very low heat and stirring in 1 to 2 teaspoons warm cream or milk (or a small knob of butter). It may smooth out, but results vary depending on how overheated or seized it got.
Why is my fudge too soft to slice?
Common culprits: not enough chocolate, using an off-brand low-fat or fat-free condensed milk, or not chilling long enough. Make sure you use a full 14-ounce can of sweetened condensed milk and 3 cups chocolate chips (or 18 ounces chopped chocolate). Chill at least 2 hours. If it is still soft, refrigerate overnight.
Can I make this in the microwave?
Yes. Microwave in short bursts and stir well between each round. Chocolate holds its shape even when it is hot, so stirring is how you find out what is actually melted.
What mix-ins work best?
Keep it simple and dry: toasted nuts, crushed pretzels, mini marshmallows, chopped cookies, or a swirl of peanut butter. Add mix-ins after the fudge is smooth and off the heat so they do not melt and disappear.
Can I use a different pan size?
Yes. An 8x8-inch pan gives you thick, classic squares. A 9x9-inch pan works too, but the fudge will be a bit thinner and may set a little faster.
What chocolate works best?
Semisweet chips are the most reliable and balanced. Chopped semisweet baking chocolate melts even smoother. Milk chocolate is sweeter and tends to set softer, so if you use it, consider mixing it with semisweet (half and half) for a firmer bite.