How to add a sub-recipe to a main recipe

How do I add a sub-recipe to a main recipe?

1. Open the recipe and, under Ingredients, click + Add new ingredient.
2. Switch to Sub-recipes and choose the one you want — the steak sauce, say.
3. Enter the amount the dish uses — e.g. 200 ml.
4. Click Save.

The cost takes care of itself: if the sauce batch makes 2.5 L and the dish uses 200 ml, the dish is charged 8% of the batch cost. There's nothing else to work out — no "portions per batch" arithmetic — because the sub-recipe already knows its yield.