You don't need a monostable to hold it off, you just need one to hold it on for a few seconds. See below.
The Schmitt trigger gives a fast negative edge when sufficient light hits the photocell. This edge is differentiated by C1 and R1, and triggers the 555 monostable. The monostable pulse width is adjustable to about 10 seconds max. You can make it longer by increasing the value of C2. It will not fire again until the light level drops well below the threshold, and then rises again to the threshold - generally next morning, unless you have an eclipse or a really dark cloud pass over.
The optional LED is mostly for troubleshooting. It will be a needless drain on your battery, if you have one. An LED and resistor from 555 output to GND might also help in troubleshooting.
If you don't have a CD40106, but you do have another 555, you could use it as a Schmitt trigger instead.
BTW, I haven't built this or simulated it, so it may have errors. Hopefully, some of the other trolls here will review it and catch any mistakes.