On the KubeJS recipes event, there is a method named forEachRecipe which allows you to access the recipe ingredients and output of any crafting type. Ive tested it on minecraft:crafting_shaped and received a table, as expected however when trying it on tfc:quern the output will be available but the ingredients are consistently an empty table [].

Here's a code snippet to reproduce the issue

  event.forEachRecipe({ type: 'tfc:quern' }, recipe => {
    let ingredients = recipe.originalRecipeIngredients;
    let output = recipe.originalRecipeResult;
    console.log(ingredients)
  });

This is due to TFC itself. By default, RecipeJS#getOriginalRecipeIngredients() delegates to Recipe#getIngredients(), which defaults to an empty list.

TFC's quern recipe is a SimpleItemRecipe, itself a child of ISimpleRecipe, a child of vanilla's Recipe. Neither of those two recipes override #getIngredients() to return the single input.

In the next update, I'll look over all of TFC's recipe types and override RecipeJS#getOriginalRecipeIngredients() and RecipeJS#getOriginalRecipeResult() as needed. Thanks for the report!

This functionality has been released with 1.3.2, enjoy!