To make creme pâtisserie, stir milk, cream, sugar and vanilla seeds in a saucepan over low heat until sugar dissolves and mixture is hot.
Whisk egg yolks and flour in a bowl until smooth and combined. Gradually whisk in hot milk mixture in a thin steady stream.
Return mixture to saucepan over low heat and cook, stirring, until thickened. Pass through a fine sieve into a bowl. Cover surface with plastic wrap and refrigerate until cold.
Blend raspberries until smooth and pass through a sieve. Fold in whipped cream. Fold mixture into creme pâtisserie in two batches. Refrigerate until cold.
To make choux pastry, place butter and 250ml (1 cup) water in a small saucepan over medium heat. Bring to the boil, then remove from heat. Add flour and salt. Beat with a wooden spoon until mixture leaves side of pan and a smooth ball forms. Set aside for 5 minutes to cool. Beat in eggs, one at a time and beating well after each addition, until mixture is thick and glossy.
Preheat oven to 220C and grease and line two large oven trays.
Spoon mixture into a piping bag fitted with a round nozzle. Pipe 10cm lengths onto prepared trays.
Bake for 15 minutes or until puffed and golden. Reduce oven to 160C and bake for a further 15 minutes or until crisp. Turn oven off. Using a serrated knife, cut eclairs in half. Return to oven for 10 minutes or until dry. Cool.
Dip top half of each eclair in melted chocolate. Decorate with blueberries and pistachios and set aside to set.
Spoon or pipe creme pâtisserie into remaining eclair halves and finish with chocolate-topped half. Serve.