Preheat oven (electric cooker: 225 °C/circulating air: 200 °C/gas: level 4). Wash shrimps and pat dry. Peel garlic and cut into slices. Heat 1 tbsp. oil in a frying pan. Fry the prawns for 3-4 minutes, turning them over.
Fry the garlic briefly. Season with salt and pepper. Leave to cool.
First cut the bread in half crosswise, then cut through horizontally. Sprinkle with 2-3 tablespoons of oil. Roast in a hot oven for 5-10 minutes until golden brown.
For the sauce, wash and dry the lemon and grate some peel. Squeeze the lemon. Mix mayonnaise, sour cream, 3 tablespoons lemon juice and zest. Season with salt, pepper and 1 pinch of sugar.
Stir in the capers.
Clean, wash and spin dry the salad and cut into coarse strips. Halve the avocado, stone it, remove the flesh from the skin and cut into pieces. Sprinkle with the rest of the lemon juice.
Mix prawns, avocado, salad and caper mayonnaise. Spread over the bread halves.