Line an 8 x 8-inch square tin with parchment, allowing a 1- to 2-inch overhang on all sides. Spray generously with nonstick spray.

Melt the butter in a large, heavy-bottomed saucepan or stock pot over medium heat.

Add the rose marshmallows, and continue stirring until completely melted.

Remove from heat. Stir in the powdered freeze-dried raspberries, rosewater, and fine sea salt.

Stir in the puffed rice cereal. Continue stirring until well-combined, with no dry cereal remaining.

Pour into prepared tin.

With damp or oiled fingertips, press down gently until evenly distributed. (Do not pack the cereal mixture too firmly, or the treats will be difficult to slice.)

Set aside and allow to cool at room temperature, at least 30 minutes or until cool to the touch.

Ganache:

Melt the white chocolate over a bain marie, or double boiler.

In a separate saucepan, warm the cream over low heat. Do not boil.

Whisk the warm cream into the melted chocolate. Continue whisking briskly until ganache turns thick and creamy.

Pour ganache over cereal layer.

With a small stepped palette knife or rubber spatula, spread ganache evenly over entire surface.

Sprinkle with dried rose petals.

Refrigerate 1 hour, or until ganache sets. Slice into squares and serve.

Layer leftover treats between sheets of parchment. Store in an airtight container at room temperature for up to 3 days.