[2.8.73] Custom Recipes How-to

The IC2 jar is just a glorified zip, so you can open it with something like 7zip or WinRar. In the assets/ic2/config directory within it you have all the recipe configs which IC2 uses. To modify them you copy the ones you want out of the jar into a folder called ic2 in the config folder (which you have to make yourself). Once you've done that you can open the ini files using any text editor, and they have both explanations of the format at the top and all the recipes IC2 adds as examples below. To add a custom recipe you just add lines into that file which IC2 will use instead of the one in the jar. Any lines you remove from there will also remove the recipes from the game if you wanted that too.

The normal recipe override location in config/ic2 applies over the top of whatever profile is selected. So if you want custom recipes that are different between profiles then you'll have to create your own profiles that extend the profile you want them to work with. Taking a simple example of adding more shapeless recipes to classic and replacing the shaped ones all together:

<profile>
    <!-- Profile name -->
    <name>More Classic</name>
    <!-- Defines a texture override for the given mod -->
    <!-- Can also point to a directory and apply to other mods, but for this purpose we'll use the special value of OLD for IC2 -->
    <textures>OLD</textures>
    <!-- Set the blocks/items which are enabled or disabled -->
    <!-- Options are NEW, OLD and BOTH -->
    <style type="OLD" />
    <!-- Recipe change options for the crafting table -->
    <crafting>
        <shaped>
            <!-- Define ini files which represent the shaped crafting recipes we want to use -->
            <replacements>
                <!-- The path is relative to the profile.xml (ie this) -->
                <file path="my_classic_shaped_recipes.ini" />
                <!-- As many files as you like can be here -->
                <!-- It can even be empty if you want to remove everything from it -->
            </replacements>
        </shaped>
        <shapeless>
            <!-- Extend takes all the changes from the given profile -->
            <!-- Thus this is effectively extending all the Classic default profile does -->
            <!-- (Which can be found in ic2/profiles/classic in the IC2 jar) -->
            <extend profile="Classic" />
            <!-- Additions are ini files which are also loaded in to add recipes from -->
            <additions>
                <file path="Extra shapeless recipes.ini" />
            </additions>
        </shapeless>
    </crafting>
</profile>

That profile.xml file can go in a folder or a zip within an ic2_profiles folder in the root of your minecraft instance (ie the same place where mods, config, logs, etc. is in). The file paths can go in the same structure with as much nesting as you want, the sample above would have them in the same level as the profile.xml itself.

Additional profiles are selected within the main IC2 config by their name, which is case insensitive. Duplicate profile names will log a warning and continue to use the first profile registered with the name. If the profile in the config can't be found it will log a warning with all the profiles it has managed to load and will continue using the default (Experimental).

This still needs some more formal documentation for defining all the possible options for what you can do, but the classic profile within the IC2 jar has a wide range of them as a pre-existing example.