Rhubarb Upside-Down Cake with Rosemary Caramel Sauce

Ingredients

• 2 teaspoons double-acting baking powder 
• 1.3 cups cake flour 
• 3 ounces chocolate such as callebaut white chopped
• 2 large egg whites at room temperature
• 0.5 cup granulated sugar 
• 1 cup granulated sugar 
• 8 servings sauce 
• 8 servings cream chamomile ice cream sour
• 0.5 teaspoon juice of lemon 
• 0.5 cup brown sugar light packed
• 0.5 cup milk 
• 0.5 pound rhubarb cut into 1/2-in. slices (2 cups)
• 0.5 pound rhubarb split cut into 2-in. pieces
• 1  rosemary sprig (5 in.)
• 0.5 teaspoon salt 
• 0.3 cup butter unsalted at room temperature
• 0.8 teaspoon vanilla extract 
• 1 cup whipping cream 
• 8 servings compote 
• 8 servings compote 

Equipment

• bowl
• frying pan
• baking sheet
• sauce pan
• baking paper
• oven
• whisk
• blender
• ramekin
• toothpicks
• spatula
• slotted spoon

Directions

1. Preheat oven to 35
2. Make cake: Butter a 9-in. round pan or 8 (1-cup) ramekins and line with parchment paper or waxed paper cut to fit. Butter the paper. In a bowl, toss rhubarb with 3 tbsp. granulated sugar. Spoon evenly into pan or ramekins; if using ramekins, set on a rimmed baking sheet.
3. Melt chocolate in a small metal bowl over a pan of barely simmering water, whisking until smooth, 2 to 4 minutes.
4. Let cool.
5. Beat butter and 1/2 cup granulated sugar in a bowl with a mixer until fluffy.
6. Add egg whites and vanilla and beat until well blended.
7. Combine flour, baking powder, and salt in another bowl. Beat flour mixture into egg mixture half at a time, alternating with milk, until smooth. Stir in chocolate.
8. Spread batter evenly over rhubarb.
9. Bake cake until golden brown and a toothpick inserted in center comes out almost clean, 28 to 35 minutes.
10. Let cool in pan or ramekins about 30 minutes.
11. Heat cream and rosemary in a small saucepan over medium heat until bubbles form at edge of pan, stirring occasionally, 3 to 5 minutes.
12. Remove from heat and discard rosemary.
13. Stir granulated sugar with lemon juice and 2 tbsp. water in a 12-in. frying pan. Cook over medium-high heat, occasionally picking up pan and swirling mixture around sides to wash down sugar crystals, until deep golden, 5 to 6 minutes. Immediately remove pan from heat, add cream (it will bubble up), and whisk until smooth. Scrape sauce into a serving bowl.
14. Make compote: In a small saucepan over medium heat, bring brown sugar, 1/3 cup water, and the rhubarb to a boil, stirring occasionally. Reduce heat and simmer until rhubarb is tender, 4 to 5 minutes.
15. Loosen cake from sides of pan or ramekins with a small metal spatula. Invert pan onto a platter (or invert ramekins onto dessert plates) and remove paper. For cake on platter, cut into wedges and transfer to plates. Using a slotted spoon, spoon compote and some syrup on cake. Spoon some sauce next to cake and serve the rest on the side.
16. Serve with chamomile ice cream.