Adding malt powder to a conventional brown bread machine recipe
As it's really hard for us here on Seasoned Advice to quantify a memory from your youth, please experiment using the binary empirical method:

start with one spoon ¹
if that's not malty enough for you, double the dose
keep doubling the dose until it's too malty
then go halfway in-between the too low dose and the too high dose (E.G. if 4 is not enough and 8 is too much, take 6)
keep on halving until you get it just right (E.G in the above example: 5, 4.5, 4.25, 4.125, ...)

If you get it just right, dream of childhood memories...
:-)
¹ Obviously &quot;spoon&quot; is a non-SI unit and can be a coffee spoon, tea spoon, table spoon or even a ladle depending on the size of the bread and how malty your memory of the Granary bread reallly is...  ;-)