Preheat the oven to 200C/400F/Gas 6.
Heat a griddle pan until very hot.
Season the turkey breast, to taste, with salt and freshly ground black pepper, then rub with the oil.
Place the turkey breast onto the griddle pan and cook for 2-3 minutes on each side, or until golden-brown griddle marks appear on both sides.
Transfer to the oven and cook for 8-10 minutes, or until completely cooked through.(The chicken is cooked through when the juices run clear when pierced in the thickest part with a skewer.) Remove from the pan and set aside to rest. Slice into ten thin slices, then cut each slice in half.
Meanwhile, heat the grill to its highest setting.
Place the streaky bacon underneath the grill and cook on both sides until crisp and golden. Allow to cool, then cut the bacon into three equal pieces.
For the guacamole, place the avocado into a bowl and mash to a paste with a fork.
Add the garlic, lemon juice and a drop of Worcestershire sauce and mix well.
Using a 5cm/2in square pastry cutter, cut out 20 squares from the pumpernickel.
To serve, place a spoonful of guacamole onto each square of pumpernickel. Place a piece of bacon on top of the guacamole, then arrange two pieces of turkey on top. Place a small dollop of cranberry sauce onto the turkey and serve.