1. Bring to a boil and simmer until shrimps are cooked. Transfer into a food processor and process until the shrimps are coarsely chopped. Set aside.
2. In a skillet heat 1 tbsp olive oil. Fry onion, shrimps from step #1, mushrooms and corn until wilted. Then add salt to season.
3. Add the butter and stir until completely melted, then add flour while stirring. Little by little add milk, it will gradually thicken the mixture. Add sour cream. Put all the ingredient A to season. Mix well.
4. Let the mix cool down in the freezer until firm (about 1h).
5. Shape the mixture into round balls with a slightly flattened bottom, dip in the flour, then beaten egg and coat with breadcrumbs.
6. Add the croquettes into the hot oil in batches, cook over medium-low heat until both sides are nicely browned. Remove from the oil and drain on paper towels.