Begin by oiling/greasing the dishes you are going to use, all ready for using immediately, when the fudge is cooked. (photos before the recipe card for ways to grease silicone and metal tins). You can also use some cling film/plastic wrap on top of the greased dishes, such as for metal tins.
Break up the chocolate & into a large microwave-safe bowl before popping in the microwave for 1 minute (at the most). (See notes on bowls to use). Mix the chocolate around (even if it doesn't look like it's melting), & microwave for 30 seconds.
Mix again & in doing so the heat of the bowl & movement will result in more melting of the chocolate. If all melted proceed to the next step. Depending on the power of your microwave, the time taken to completely melt will vary. If needed, continue cooking for 30 second bursts, mixing well in-between each time, until completely melted. Never go any higher than 30 seconds for melting chocolate in the microwave or you can ‘burn’ the chocolate and made it hard. (For 400g/14 oz of chocolate, 60 seconds at the beginning is fine).
Immediately add the cubed butter, mixing well until all melted & combined. See Photo 1 above.
Then add in the tin of condensed milk, mixing through before popping back in the microwave & cooking for another 30 secs.
Mix this fudge mixture really well, & microwave again for a further 30 seconds. The mixture will be starting to thicken after each 30 seconds.
Continue mixing & cooking for 30 second bursts until the mixture starts to come together & is coming away & stopping sticking to the sides of the bowl (this happens with a plastic bowl). See Photo 2 above, for how the mixture will look. (And Photo 3 below). It should be extremely hot at this point, and almost bubbling. If you want to be super precise, you are looking for a temperature of at least 105 °c (220 °f for microwave fudge). **Click Photo 2 and then pinch to zoom in
Add in the sieved icing/powdered sugar & mix until all combined.
If adding nuts etc, do so right now. For this batch in the photos, I split into 3. A third was plain fudge flavour, a third had orange extract added, and the final third had Bailey's added to it. Some I added cranberries or chopped walnuts to the fudge mixture. See Photo 3 above.
And some I topped with nuts, chopped cookies and chocolates (Malteseres/Malt balls and Toffifee). **If dividing the mixture up, I recommend to place the ones you are not working on yet, back into the warm microwave to sit.)
Once you have added your extra flavours or fruits/nuts, spoon into the prepared tin/dish, and using clean hands (or gloves is handy), press the fudge mixture into place. Smooth down as best you can and be sure to push into the sides of the dish. I was using a larger metal tin than normal, and had made a divider card, which was also handy to straighten the edges of the fudge mixture. (see Photo 4 above where it is dividing the tin). At this stage you want to also add any more nuts or cookie pieces etc, into the top-most part of the fudge. Then grab your 2nd portion of the fudge mixture and repeat till all fudge has been placed in the dishes for setting. You will notice that as time goes on, it will be beginning to get firmer.
Cover with a lid or cling film/plastic wrap and refrigerate for at least 3 hours. The fudge will look set before this but leaving as long as possible makes removal & cutting much easier.
Once set, turn out onto a chopping board, tap until the fudge comes out. Cut with a sharp knife into whatever sizes you like. Run a butter knife all around the sides if removal isn’t easy. Using cling film/plastic wrap is usually much easier. See Photo 5 above.