Preheat oven to moderate (170 degrees celsius, fan-forced) and place a large baking tray filled with water on the bottom shelf.
Grease tins well (use standard muffin/cupcake tins - recipe makes 20 muffin-size puddings - or bar tins - use two approx 24 x 14cm tins).
Combine chopped dates, bicarb soda and water in a saucepan and bring to the boil. Simmer for one minute and then set aside to cool.
Cream butter and sugar in stand mixer and add vanilla extract.
Add eggs one at a time, beating on med-high for 1-2 minutes after each addition.
Add date mixture (it doesn't need to be completely cool but shouldn't be hot) and mix on low-medium speed for one minute.
Gradually add sifted flour and mix using lowest speed until completely combined. The mixture will be quite runny.
If using (2 x) bar tins, pour half of mixture into each tin.
If using muffin tins, fill each pan only two thirds full.
Cover tins loosely with foil.
Place onto middle shelf in oven and bake for 35 minutes (for bar tins) or 30 minutes (for muffin tins). Make sure there is still plenty of water left in the baking tray on the lower shelf.
Once cooked, allow to cool a little for a few minutes and then gently ease the puddings from the tins, using a butter knife if necessary to separate the sides of the puddings from the tin.