The griottines cherries are small red cherries, pitted and kept in a Kirsch syrup.
If you intend to buy: The griottines cherries is a specialty of the region de Fougerolles, in France. They are found in jars of various sizes.
If you want to use it: Generally you must drain the griottines cherries before using in a bakery for example, but in contrast with an ice cream or a pudding, flavored syrup that accompany them is a great addition.
By "mash powder" do you mean mash potato powder?
If so, yes you can, see how to on this chicken recipe : chicken breasts in a potato crust.
Can I use potentiometer mash powder to make cutlets?