Preheat oven to 180 C / Gas 4. Combine the milk and lemon juice and set aside to curdle for 5 minutes.
In a mixing bowl add all the remaining ingredients except for the chocolate. Slowly knead the biscuit dough while gradually adding the milk mixture. Wrap the dough in cling film and chill in the fridge for at least 10 minutes.
On a floured work surface, roll out the dough to about the thickness of a pound coin (you can increase or decrease the thickness if desired, but baking time will vary. Keep in mind they'll rise slightly when baked). Dip a heart-shaped cutter in flour, stamp out the biscuits, then place on a baking tray lined with parchment. Re-roll any scraps of dough and repeat.
Bake the biscuits for 10 to 15 minutes. Once done take them out of the oven and let them cool for at least 15 minutes in a cooling rack before dipping them in chocolate.
Place the chopped chocolate into a glass bowl and microwave for 70-80 seconds. Chocolate easily burns, so make sure they are not overheated. At this stage, most of the chocolate chunks should melt. Take a spoon and start stirring the melted chocolate. This way the rest of the unmelted chunks will melt, too. If not, reheat for a couple of seconds to get the perfect consistency.
Cover a tray with greaseproof paper. Submerge the biscuits in the chocolate one at a time. Use a fork to remove the biscuits from the sauce, then tap them on the side of the bowl to remove any excess chocolate, and place them on the tray. Repeat the process until all the biscuits are covered.
Use your imagination to decorate the biscuits as desired. For example, I dusted mine with some dessicated coconut. Keep them plain if you want to.
To set, chill the biscuits in the fridge for about 30 minutes, then they're ready for munching!