Like scents, the tastes of specific foods can take me straight back to moments in my life in an instant, memories instantly jolted back to the present day. The soup we had at our wedding breakfast, the bean stew we lived on as poor but loved up graduates, the first meals we cooked in new homes, delicious dishes tasted for the first time on holday - they all mean something.
Collect together 5-10 of your favourite recipes from your relationship and write them out on an index card. Decorate however you please before mounting them in a beautiful note book or scrap book (I used one of these from Muji) then below, add your memories (or even photographs) surrounding that particular meal or dish.
You can execute this whichever way best suits your style for very little expenditure at all. Consider using items you already have such as ribbon scraps, pieces of wrapping paper, newspaper, fabric, labels from food tins, pictures from holiday brochures etc. - make it about your relationship and your memories together.
Leave plenty of space so you can continue to add more memory recipes as the years of your relationship unfold.
P.S. I've collected together a selection of the best free printable Valentine's cards make sure you check them out.