Cut lemongrass into very fine slices from the root (only up to the purple inner part), crush and knot the rest of the grass. Cut 10-12 very fine slices of galangal, crush the rest (as you do with garlic cloves).
Lightly crush and quarter the shallots. Quarter 1 bergamot leaf, roll 1 and cut into very fine strips. Crush the chilli, quarter the tomato, cut the oyster mushrooms into strips
Heat broth, add herbs (lemon grass, galangal, shallots, bergamot leaves, coriander, chillies), allow to boil down briefly.
Add tomato and oyster mushrooms and salt. Add the shrimps and cook until they are cooked. Remove from heat, add lime juice, fish sauce, coffee cream and chilli paste.
Remove lemongrass knots, crushed galangal root, crushed shallots from the soup (these are not eaten)
Garnish with a coriander branch and serve.