Hard biscuits happen because of a loss of moisture, whether from overcooking, improper storage or just age. In most cases, you can breathe life back into hard biscuits with a few tricks. To get some softness back into your biscuits, you need to replace lost moisture, and the best way to do that is with heat.
Individual Biscuits
Heat one or two biscuits into the microwave for 20 to 30 seconds. Touch them to check for softness. For very hard biscuits, skip this step and go directly to the next step.
Wrap cooled biscuits in a slightly damp kitchen towel and heat for 20 to 30 seconds. Do this also if the initial heating didn't sufficiently soften them.
Store the biscuits in a tightly sealed plastic bag with a slightly damp paper towel inside. Overnight, the remaining biscuits may soften up without having to heat them. Change the paper towel daily.
Multiple Biscuits
Preheat the oven to 200 degrees Fahrenheit.
Spread out the biscuits on a flat baking sheet pan.
Moisten a clean kitchen towel and wring out as much water as possible.
Place the kitchen towel over top of the biscuits, then place them in the oven.
Check the biscuits for softness about every three minutes. Wet the towel again if it dried out before the biscuits heated through. Remove the biscuits if they're not soft after 20 minutes, as they'll likely not get any softer.