Turn on the grill. Put the bacon on a tray and grill on both sides until it is nice and crisp. Leave it to cool and then break into pieces.
Bring saucepan of water to the boil and cook the beans for 4 minutes. Drain and then hold them under cold running water for a few seconds to stop them cooking any further.
Put the spinach in a large bowl and add the beans, bacon and shallots. Halve the avocados, then cut into cubes and add them to the bowl of salad.
Mix the brown sugar and garlic in a small bowl. Add the rest of the ingredients and whisk everything together to make a dressing.
Pour the dressing over the salad and toss well. Grind some black pepper over the top and sprinkle with some salt.