Whether your church is celebrating its own birthday or a church member is having a birthday party at church, a stained-glass cross is an excellent choice for the cake. This cake looks fabulous, but isn't terribly difficult to cut out and decorate. Black icing gives the stained glass finish the appearance of lines of lead separating the panes, while an assortment of beaten jellies take the place of brightly coloured glass.
Cut the rectangular cake in half lengthwise. Cut one of the halves into thirds, cutting at a right angle to the original lengthwise cut. Leave the topmost of these thirds in place to form one arm of the cross. Move a second of these thirds into position to form the opposite arm. Move the last third, so it extends the length of the half cake section.
At this point your cake will be arranged to resemble a cross.
Separate the pieces enough to spread a thick layer of white icing on both surfaces wherever cake parts are joined. Move the pieces back into position. The icing should glue them together. Set aside 1/3 cup of the white icing; use the rest to frost the top and all sides of the cross shape.
Use a toothpick to transfer a small amount of black paste food colouring into the reserved icing. Stir it thoroughly with a spoon. If the black is not dark enough to resemble lines of lead, use a clean toothpick to transfer more food colouring and stir again.
Use a clean toothpick to trace lines on the cross, making flower and leaf shapes to resemble the pattern on a stained glass window. Attach the writing tip to the piping bag and fill the bag with the black-tinted icing. Pipe thin lines everywhere you marked. These will become like lines of lead, appearing to separate panes of stained glass in your finished cross cake.
Put each kind of jelly into a separate bowl and use the electric hand mixer to thoroughly beat each of them. Wash the beaters between each kind of jelly. This will remove lumps, so that when you spread the jelly, it will look like glass.
Gently spoon jelly into the different sections outlined in black on the cake. Use mint jelly for the leaves, grape jelly for the flowers, and apple jelly for the sections in between. Carefully smooth the jelly so they fill the outlined sections. Try not to let the piped black lines get covered in jelly. They look best if they stand out.
Allow the cake to sit for at least an hour, so the jelly can air dry.