Preheat the oven to 325°F. Spray an 8-inch square baking pan with gluten-free nonstick cooking spray.
Put the chocolate and butter into a large bowl and place over a pan of simmering water, stirring regularly, until melted. Add the dry ingredients to the chocolate and stir well to combine. Beat the eggs in a separate bowl, then pour into the batter and mix until you have a silky consistency.
Spread the batter evenly into the prepared pan. Bake for 20 minutes. Remove from the oven and let cool completely on a wire rack.
While the brownies are baking, make the orange jellies. Place the water and sugar in a saucepan over low heat and stir until the sugar dissolves. Add the gelatin and stir until dissolved. Remove from the heat and add the orange juice and zest. Pour into 6 individual trifle dishes or dessert glasses, add orange slices, and place in the fridge until set, about 30 minutes.
Meanwhile, place a mixing bowl in the freezer for about 30 minutes.
Cut the cooled brownies into small squares and add them to the trifle dishes.
Pour the heavy cream into the chilled mixing bowl. Using an electric hand mixer, beat the cream. When the cream starts to thicken, add the sugar. Beat until soft peaks form and the cream is just thick enough to hold its shape.
Add the whipped cream to the trifle and top with dark chocolate shavings. Serve immediately.