In the bowl of a stand mixer fitted with the paddle attachment, beat flour, yeast, and salt at low speed just until combined. Add warm milk, 3 tablespoons (63 grams) honey, egg, and vanilla, and beat until a shaggy dough forms. Switch to the dough hook attachment. Add ¼ cup (57 grams) butter, and beat at medium speed until a smooth, tacky dough forms and pulls away from sides of bowl, 10 to 12 minutes. Turn out dough, and shape into a smooth ball.

Spray a large bowl with cooking spray. Place dough in bowl, turning to grease top. Cover and let rise in a warm, draft-free place (75°F/24°C) until doubled in size, about 45 minutes.

In a small saucepan, combine sugar, cream, remaining ¼ cup (57 grams) butter, and remaining 2 tablespoons (42 grams) honey. Heat over medium-high heat, stirring frequently, until butter is melted and sugar dissolves. Remove from heat, and fold in sliced almonds.

Spray a 10-cup Bundt pan with baking spray with flour. Pour sugar mixture into prepared pan, using a spoon or spatula to spread and level mixture.

Punch down dough, and turn out onto a clean surface. Pat or roll into an 18x8-inch rectangle, pressing down to completely flatten dough and pop any remaining air bubbles. Starting at one long side, roll dough into a tight rope, firmly pressing dough as you roll; pinch seam to seal. Shape dough into a ring, with seam on inside of ring. Place dough, seam side facing inside of pan, in prepared pan. Cover and let rise in a warm, draft-free place (75°F/24°C) until puffed, 30 to 45 minutes.

Preheat oven to 350°F (180°C).

Bake until golden brown and an instant-read thermometer inserted near center registers at least 190°F (88°C), 25 to 30 minutes. Let cool in pan for 10 minutes. Invert cake onto a wire rack, and let cool completely.

Using a large, serrated knife, cut cooled cake in half horizontally. Slide top half onto a cake board or plate to move. Spread Custard Filling onto bottom half of cake. Slide top half of cake on top of filling. Refrigerate for 30 minutes before serving. Best served same day.