Boil water and sugar in a saucepan until the sugar has dissolved
Rinse the sea buckthorn and pick them of the twigs (if this has not already been done)
Pour the sea buckthorn and vanilla into the sugar solution and cook for 10-15 min until the sea buckthorn has been wrinkles and the water is orange/yellow
Pour the contents of the pot into a blender and blend until the sea buckthorn is no longer whole
Arrange a large bowl with a strainer and a cloth (cheesecloth or dishtowel) on top
Pour the blended sea buckthorn through the cloth and the strainer - use a spoon to mash the last bit through the cloth (throw out the dry matter that remains in the cloth)
Bottle and store in the fridge or a cold cellar