Dark Chocolate Fridge Cake

1. Grease the bottom and sides of an 8-by-8-inch baking dish with butter. Line with parchment paper, allowing for a 2-inch overhang on all sides.
2. Add the butter and chocolate into a large mixing bowl. Set the bowl over a saucepan of barely simmering water over low heat. Gently melt, undisturbed, until mostly melted. Remove the bowl from the saucepan and stir until the chocolate is melted, silky and smooth. (Alternatively, you can melt in the microwave in 20 second increments.)
3. Into the bowl of melted chocolate, add the shortbread, marshmallows, pretzels, pistachios and gummy worms. Toss to completely coat, then transfer to the greased baking dish, pressing down with a rubber spatula to make the mixture as smooth as possible. Sprinkle with flaky salt. Refrigerate until completely chilled and hardened, at least 30 minutes, or up to overnight.
4. Remove the cake from the baking dish by using the parchment handles. Place on a cutting board and remove the parchment. Cut into 16 even squares. Serve immediately or refrigerate in an airtight container for up to 5 days.

Hibiscus Almond Marshmallows:

1. Grease an 11-by-7-inch baking dish with vegetable oil cooking spray. Set aside.
2. In a small bowl, combine the cornstarch and powdered sugar. Coat the prepared baking dish with half of the powdered sugar mixture. Pour any excess mixture back into the bowl.
3. In a small saucepan, bring 1 cup of water to a boil over medium-high heat. Add the hibiscus leaves, turn off the heat and steep, covered, 20 minutes. Strain out the hibiscus leaves and measure out the remaining hibiscus-water (there should be about 3/4 cup remaining. If not, either supplement with tap water or pour some out to yield 3/4 cup.) Chill in the refrigerator to cool completely.
4. To make the almond marshmallow layer: In the bowl of a stand mixer fitted with the whisk attachment, combine 1/2 cup of water (not the hibiscus water, just plain water) and the vanilla and almond extract. Sprinkle 2 envelopes of the gelatin over the liquid to bloom.
5. In a small saucepan, stir together 3/4 cup of the granulated sugar, 1/2 cup of the corn syrup, 1/8 teaspoon of the salt and 1/4 cup more water (again, not the hibiscus water, just plain water). Attach a candy thermometer to the saucepan. Heat the mixture over medium-high heat until it reaches 240 degrees F, then immediately remove from the heat and bring it over to a stand mixer fitted with the whisk attachment.
6. Turn the mixer on low speed and drizzle in the corn syrup mixture in a slow and steady stream down the side of the bowl. Once the entire mixture is in, gradually increase the speed to high and let it mix for 7 to 10 minutes total, until lukewarm and fluffy. While the mixer is running, grease a rubber spatula and have that standing by the mixer, as well as the prepared pan. Using your greased spatula, immediately scrape the marshmallow mixture into your pan and spread it out evenly as best you can with the spatula. Set this aside while you make the hibiscus marshmallow layer.
7. Clean and dry your mixer bowl, whisk attachment, spatula and small saucepan.
8. Now, make the hibiscus marshmallow layer: Repeat the process but use the hibiscus water this time! In a stand mixer fitted with the whisk attachment, add 1/2 cup of the hibiscus water and then sprinkle the remaining 2 envelopes of gelatin over the liquid.
9. In a small saucepan, stir together the remaining 3/4 cup granulated sugar, 1/2 cup corn syrup, 1/8 teaspoon salt and 1/4 cup hibiscus water. Clip on a candy thermometer. Heat the mixture over medium-high heat until it reaches 240 degrees F, then immediately remove it from the heat and bring over to the mixer.
10. Turn the mixer on low and drizzle the corn syrup mixture in a slow and steady stream down the side of the bowl. Once the entire mixture is in, gradually increase the speed to high and let it mix for 7 to 10 minutes total, until lukewarm and fluffy. While the mixer is running, grease a rubber spatula and have that standing by the mixer, as well as the pan with the almond layer.
11. Using your greased spatula, immediately scrape the mixture into your pan and spread it out evenly as best you can with the spatula. Dust the top with about half of the remaining powdered sugar mixture.
12. Let set for at least 1 hour. Cut into squares and dust the edges of the squares with the remaining powdered sugar mixture.