Line a 24-cup mini muffin tin with mini cupcake liners or use a silicone mold.
Crush biscuits to a fine, even crumb. Mix with melted butter, sugar, and salt until it resembles damp sand and holds when pressed.
Spoon 1 heaped teaspoon into each cup. Press firmly with the back of a small spoon until compact and even. Refrigerate while making the filling.
Blitz freeze-dried raspberries to a fine powder. Sieve to remove seeds.
Beat fully softened cream cheese on medium speed for 2–3 minutes until completely smooth. Scrape down twice.
Add sifted powdered sugar. Beat until light and fluffy.
Add vanilla, lemon juice, and lemon zest. Beat until incorporated.
Add raspberry or beetroot powder. Beat until color is completely uniform with no streaks.
In a cold bowl, whip cold heavy cream with cream of tartar to firm peaks.
Fold whipped cream into cream cheese mixture in three additions using a rubber spatula. Fold gently — do not stir or beat.
Pipe or spoon filling into each prepared cup to the top. Smooth the surface.
Tap the tin gently on the counter. Cover and refrigerate at least 3 hours or overnight.
Just before serving, whip cold cream with powdered sugar and vanilla to firm peaks. Transfer to a piping bag with a star tip.
Remove bites from fridge. Release from molds or peel liners carefully while fully cold.
Pipe a rosette of whipped cream on each bite. Scatter freeze-dried raspberries, add fresh raspberry or white chocolate curl if using. Dust lightly with extra raspberry powder.
Serve immediately or return to the fridge for up to 2 hours before serving.