Preheat the oven to 180°C (gas 4) and 160°C (fan). In a pestle and mortar, grind the flax seeds until fine. Place in a small bowl. 3 tbsp water, stirred in and put aside for a few minutes until thickened.
Meanwhile, combine the dates and dairy-free spread in a small pan. Bring 150ml water to a boil in a separate pot. Remove from the heat once the spread has melted and mix in the bicarbonate of soda, which will froth up a bit.
In a large mixing bowl, combine the self-raising flour, light muscovado sugar, and a pinch of salt. Combine the date mixture (including the liquid), swollen ground flax seed, and vanilla extract in a mixing bowl. Blend until completely smooth. Fill a deep, oiled 22cm circular baking dish halfway with the mixture.
To make the sauce, combine the dark brown muscovado and almond milk in a saucepan and heat until the sugar has dissolved. Pour the mixture over the dates in the baking dish. Bake for 30 minutes, or until the sauce has settled to the bottom of the baking dish and is cooked through. If desired, serve warm with dairy-free ice cream.