That is interesting, Birch sap and malt.
Need to try that. I can not get much sap from the birches in July in the Lofotens as the leaves and flowers are fully formed ( flowers in middle of making seeds) but should be fine for a glass.
How much sap for a 0.5 dl measure?
Well Janne, that's a bit like asking 'how long is a piece of string'
I usually drink my malt neat - even the cask strength (57 to 60%) - you literally just need to wet your lips with each sip
At tastings they will usually offer to 'break' the dram by adding 2,3 or 4 drops of spring water using a pipette - and yes, it does make a difference.
A professional malt taster will add twice as much water as malt (yuck) so that they can take in all the subtle flavours of the drink.
However, just for a change, I like a little spring water with my dram and then I would add about 10ml to a 50ml (Scottish Double) measure. Others add more; up to 25ml I would suggest.