Combine the pepper with the mortar to get the mortar with ground hot pepper. Turn left to the the device. Use the decanter with some wish-wash on the cauldron. Use the mortar with ground hot pepper, gunpowder, gold coin, cooled lava and thermometer on the cauldron:

Select the green Done button and then use the glass retort on the tap to get the red liquid. Time travel to the black forest: