Heat the oven to 100C/215F/gas mark ¼
Line 2 baking sheets with greaseproof paper.
Beat the egg whites using an electric whisk or stand mixer in a large, spotlessly clean bowl until soft peaks form.
Add the sugar gradually, a tablespoon at a time, whisking well after each addition, until all the sugar has been added.
Continue to whisk the meringue for a few minutes more until it is very thick and glossy and forms stiff peaks when you lift the whisk out of the bowl.
In a separate bowl, whisk the jam until it is smooth then add to the bowl of meringue and very gently whisk through until smooth.
Fit a piping bag with a large plain or star nozzle (or simply snip the corner off a disposable piping bag). Turn the bag inside-out, either over a jug or vase, or I like to do it over my arm - holding the nozzle in my hand. Use a (clean!) artists paintbrush to paint stripes of the gel colouring down the inside of the bag.
Fill the bag with the meringue and twist the top closed. Use a little meringue mix to stick the greaseproof paper to the baking trays (this makes it easier to pipe) and pipe small 'kisses', slightly spaced apart on the trays, I like to do a couple of different sizes.
Bake for about 45 minutes, but be aware that they could take up to two hours depending on your oven (mine took 1 hour for teeny ones and two for larger ones). They are ready when they can be lifted off the paper in one piece - if the bottom comes away they aren't ready yet.
I found that due to the jam they still felt a little soft when they were actually done, but firmed up after being taken out of the oven. Take them out of the oven and let them sit for a couple of minutes before trying to lift them off the paper, they should have become firm and peel off the paper in one piece, if they aren't ready yet put them back in the oven for another 15 minutes then check again.
Cool and store in an airtight container.