I found in the internet very few recipes with diastatic and non-diastatic malt. So I made a few experiment, which in the end gave a very successful result.
250-270 gr fresh starter - 100%
500 gr strong bread wheat flour
300 - 320 ml water (depends on the flour)
3 - 4 gr fresh yeast
1 tbsp black-stripe molasses
½ tsp of Diax (Diastatic barley malt  from Muntons)
2 tbsp Spraymalt Light  (DMX from Muntons)
1 tsp salt
Canola oil for greasing
1 cup of raisins
1 cup of coarsely chopped walnuts
In 20 ml of warm water dissolve the yeasts.
In 300 ml of water dissolve the molasses and the Spraymalt light (pay attention that this powder is very hygroscopic).
Pour the flour in a big bowl, adding salt and Diax, our starter and our liquids. Mix all together until you get nice elastic dough. Knead a few minutes. Leave it on the table covered with a plastic cover for 10 minutes, Then "stretch and fold". Repeat operation 3 times.
Take the dough out of the bowl, wash and wipe the bowl, then grease it. Put the dough inside. Cover with greased plastic lid, and put in the fridge until the dough gets twice it's size.
Take out the dough, kneed it a little (in this stage I've added into the dough the nuts and the raisins).
Put the dough in the bread baking form (I use baking-parchment paper), cover with the plastic lid and put once again in the fridge. I left it for the whole night and it grew at least twice of it's size. Heat the oven with the oven stone to 240 C. Put the bread form with the dough inside. Usually I pour ½ cup of water directly into the oven (not on the bread) to keep the humidity. After 20 min lower the temperature to 200 C and bake for another 20-25 min.
After taking out the bread loaf cover it with cloth.
The bread has a very rich flavor, nice color and tight crumb.