Crush the digestive biscuits into fine crumbs using a food processor or by hand.
Mix the biscuit crumbs with melted butter, then press the mixture into the base and sides of a tart tin.
Chill the crust in the fridge for 30 minutes to set.
Break the dark chocolate into pieces and place in a bowl.
Heat the double cream in a saucepan until just simmering, then pour it over the chocolate.
Let it sit for a minute, then stir until smooth.
Add the butter and vanilla extract, stirring until fully combined.
Pour the ganache into the chilled crust and smooth out the top.
Refrigerate for at least 2–3 hours or until set.
Decorate with chocolate eggs, bunnies, and sprinkles before serving.