Blend the crème fraîche with the chia seeds, vanilla extract, honey, raspberries (reserving a handful of the raspberries for the garnish) and salt until smooth and well combined. Add the stevia, taking care to taste after each drop as stevia is very sweet.
Chill the chia mixture in the fridge for at least 4 hours, or preferably overnight.
To serve, divide the chia pudding equally among 4 serving bowls. Garnish with the reserved raspberries, toasted nuts and orange zest.
As an alternative to the crème fraîche you can use 80g/3oz cahsews. Put the cashews in a bowl and pour over 500ml/17fl oz of cold water. Soak for 3 hours, then drain well and rinse under cold running water.