Set oven to 180oc/GM4 and line 2 baking trays with greaseproof paper.
Beat the butter and sugar together until creamy. Add the egg yolk and zest, combine. Sift in the flour and fold through about 3/4's of the mincemeat. Stir until it starts to come together into a dough.
Pull biscuit sized lumps from the dough and pop them onto the trays, not too close together as they will spread. Press down to flatten into cookie shape, dab a little of the remaining mincemeat onto the top of each cookie.
Pop into the oven from approx 10-15 minutes, until they are golden and still a little chewy in the middle.
Wonderful warm, but just a delicious cold the next day from the cookie jar.