First of all, take a bowl and add flour, milk and vegetable oil in it. Mix all the ingredients well. Then, add sugar, baking powder, salt and egg in the mixture. Stir all the ingredients gently.
Now, take a skillet and fill it half with water. Put the crepes mixture in the skillet and place it on a low heat stove. Cover the skillet. You have to cook it until they become brown.
Meanwhile, take a saucepan and melt the butter in it by placing it on a medium heat stove. Put the mushrooms in the saucepan and add the onions. Stir the ingredients with the help of spatula. Then, add the shrimps, crabmeat and the cream cheese. Keep stirring until the cheese is melted properly.
Put around ¼ cup of seafood mixture in the centre of each crepe. Roll them up and place them in the glass baking dish. Take the Swiss cheese and sprinkle it on the crepe.
Place the crepes in the microwave and heat for around four to six minutes. When the cheese melts on the crepes, take them out of the microwave. You can sprinkle some slices of onions or garnish some black pepper on the crepe before serving. Just make sure they are cool enough to eat.