For the cheat’s rough puff, mix the flour and salt together in a bowl. Rub in the chilled butter using your fingertips, until the mixture resembles breadcrumbs.
Gradually add enough water to form a dough (about 120ml water).
Roll the dough out into a long rectangle (approx. 45cm x 15cm) on a lightly floured work surface.
Coarsely grate half of the frozen butter over the bottom two thirds of the dough. Fold down the top third and fold up the bottom third as if folding a letter.
Turn the folded dough through 90 degrees and roll it out into a rectangle again. Repeat the process of adding the remaining frozen butter and fold as before. Wrap the dough in cling film and leave to rest in the fridge for 30 minutes.
Meanwhile, peel the garlic clove and cut into quarters, lengthways. Pick 5 small sprigs of rosemary. Poke the tip of a knife into the camembert to make 9 small slits, then fill each slit with garlic and rosemary.
Heat the oven to 220°C/200°C fan/425°F/Gas 7.
Roll out the rested dough into a long rectangle and repeat the folding process, folding down the top third and fold up the bottom third as if folding a letter. Cut the dough in half, then roll each piece out into a large rectangle measuring 30cm x 40cm.
Place one of the sheets of pastry onto a piece of baking paper. Spread the cranberry sauce over the pastry, sprinkle over the bacon bits, then cover with the second sheet of pastry. Gently press to seal the two sheets of pastry together.
With the short edge of the pastry facing towards you, cut out a large triangular Christmas tree shape. Reserve any pieces that you cut off.
Gently score (be careful not to cut all the way through the pastry) 2 fine lines down the centre of the triangle, 3cm apart, to form the trunk of the tree. Using a sharp knife, cut 12 evenly spaced horizontal strips either side of the trunk, leaving the trunk intact.
Twist each pastry strip two or three times, pressing the ends into the baking paper. Slip a baking sheet under the pastry tree, brush with beaten egg, sprinkle with sesame seeds and bake for 25 – 30 minutes, until crisp and golden.
Using the pastry leftovers cut out a base for the tree, then cut a circle in the middle and place the camembert in it. Brush with beaten egg, sprinkle with sesame seeds and bake for 20 – 25 minutes, until crisp and golden.