I love the rough texture of the cement in combination with the imprints the plastic cups make.
You will need cement or tile adhesive (cement gets sold here in 50 kg bags only which was a bit more then I wanted to use, so I tried it with the tile stuff and it worked just fine), plastic cups and a bucket.
Pour some water into a bucket and then add cement (careful, it makes a lot of dust) until it has the consistency of peanut butter
Fill the cement into a plastic cup (not quite to the top) and insert another plastic cup to make an indentation for the candle
Let it dry. This is the most difficult part as it takes a couple of days and Eva got quite impatient. I did cut one open too soon and it broke apart, so give it time to dry properly
And here you have the finished product :-)