Line a mini muffin pan with 12 paper liners.
Set aside on a tray or cutting board you can move to the fridge.
In a microwave-safe bowl, combine the sugar-free white chocolate, cocoa butter, and butter (or coconut oil). Heat in 20–30 second bursts, stirring between each, until smooth. You can also melt over a double boiler on low heat.
Whisk in the heavy cream, powdered sweetener, vanilla extract, and salt.
If it looks slightly separated, keep whisking gently until it comes together. A silky texture is the goal.
Taste and adjust sweetness. If using lemon zest, stir it in now for a fresh, bright note that complements the raspberries.
Drop about 1 teaspoon of the warm white chocolate mixture into each liner to create a base.
Tap the pan lightly to level.
Place 2–3 small raspberry pieces into each cup. If your raspberries are large, tear them into halves or thirds so they sit nicely and don’t poke through the top.
Spoon more white chocolate over the raspberries to cover, about 1–1.5 teaspoons per cup. Tap again to smooth the tops.
You should have a thin but complete coating.
Refrigerate for 25–35 minutes, or until fully set. If you want a firmer snap, chill for an hour.
Peel off the liners and serve. For the cleanest edges, let them sit at room temperature for 3–4 minutes before unwrapping.