Whisk the sugar, cornstarch, and salt together in a heat-safe bowl until evenly combined.
Add the egg yolks and whisk until smooth and pale, then slowly incorporate the milk while whisking constantly.
Transfer the mixture to a saucepan and cook over medium-low heat, whisking continuously, until thick and gently bubbling.
Continue cooking for one additional minute, then remove from heat and stir in the vanilla extract.
Strain the custard into a clean bowl, press plastic wrap directly on the surface, and refrigerate until cold.
Warm the milk and butter together in a small saucepan until melted, then let cool until just warm to the touch.
Pour the milk mixture into a mixer bowl, add honey, eggs, flour, yeast, and salt, and mix until a rough dough forms.
Knead the dough on medium speed until smooth, elastic, and no longer sticky.
Place the dough in a greased bowl, cover, and allow it to rise until doubled in size.
Combine butter, honey, and sugar in a saucepan and heat until dissolved and bubbling, then stir in almonds and cool.
Grease and flour a springform pan thoroughly.
Press the risen dough evenly into the pan and gently spread the almond topping over the surface.
Cover and allow the cake to rise again until puffy and doubled.
Preheat the oven to 350°F with a rack positioned in the center.
Bake the cake until golden around the edges and bubbling on top.
Cool the cake briefly in the pan, then remove and cool completely on a rack.
Whip the cream until stiff peaks form, then loosen the chilled custard and fold the whipped cream into it gently.
Slice the cooled cake horizontally, spread filling over the bottom layer leaving a border, and replace the top layer.
Chill the assembled cake for easier slicing, or serve immediately if desired.