The Ladle is the perfect tool for mixing fluids and items inside a Mortar.
Usage
After adding items and pouring some fluid into a Mortar, hold right-click with the Ladle to stir and mix everything together. Like the Pestle, it takes a little bit of damage each time you use it.
You can shift-right-click a Mortar with your Ladle to leave it resting on the edge.
If you have Create installed, the Ladle also works on a Basin: hold right-click on one to stir its contents through any unheated Mixing recipe, no Mechanical Mixer required. Without Create, the Ladle simply works on the Mortar.