SPONGE:
Prep: Preheat oven to 400°F (200°C). Line a 10×15-inch jelly roll pan with parchment paper, leaving overhang. Lightly butter the parchment.
Yolk mixture: In a large bowl, whisk egg yolks with ¼ cup sugar until pale and ribbony (about 3 minutes). Whisk in orange zest, orange juice, and vanilla.
Meringue: In a spotlessly clean bowl, whip egg whites with salt until foamy. Gradually add remaining ¼ cup sugar and whip to glossy, stiff peaks that hold their shape.
Fold: Sift cake flour and almond flour together twice. Gently fold flour mixture into yolk mixture until just combined. Fold in cooled melted butter, then fold in ⅓ of the meringue to lighten. Carefully fold in remaining meringue in two additions, being gentle to preserve volume.
Bake: Spread batter evenly in prepared pan using an offset spatula. Bake 12-15 minutes until golden and springs back when lightly touched. The cake should just start to pull away from the edges.
Roll: While still hot, turn cake onto a clean kitchen towel generously dusted with powdered sugar. Remove parchment and trim any crispy edges. Starting from the short end, roll cake in towel. Cool completely on a wire rack (about 45 minutes).

FILLING:
In a medium bowl, whisk mascarpone until smooth. Add honey, heavy cream, orange blossom water (if using), orange zest, and salt. Whisk until light and fluffy, about 2 minutes. Taste and adjust sweetness or orange blossom water as desired.

WHITE CHOCOLATE GANACHE:
Place chopped white chocolate in a small bowl. Heat cream in a small saucepan until just simmering. Pour over chocolate and let sit 1 minute, then whisk until smooth. Let cool slightly until spreadable but not set.

ASSEMBLY:
Fill: Carefully unroll cooled sponge. Using an offset spatula, spread mascarpone filling evenly over surface, leaving a ½-inch border on all sides.
Roll: Re-roll tightly without the towel, using the parchment to help guide. The seam should be on the bottom. Wrap tightly in plastic wrap and refrigerate at least 2 hours or overnight.
Slice: Using a sharp serrated knife wiped clean between cuts, trim ends to create clean edges. Cut into 12 even slices (about 1¼ inches each).
Finish: Arrange on serving plates. Drizzle or brush tops with white chocolate ganache. Sprinkle with toasted almonds and candied orange peel. Finish with a tiny pinch of flaky sea salt on each roll.