Bring the frozen raspberries to the boil the day before and then let them cool down. Then stir in the chia seeds, and if you want, erythritol, use a small whisk. Put everything in a jar and let it soak in the fridge overnight.
The boiled chia jam can be kept in the refrigerator for about 4 days.
Mix the milk, sparkling water and egg with the hand mixer the next day. Add the flour and baking powder and whisk to form a smooth, thick batter.
Bake 2 pancakes in a hot, non-stick pan and serve with the jam.