Line a ten-cup metal bowl with plastic wrap, crisscrossing two pieces if necessary, leaving an overhang all around.
Pour 1/4 cup tepid water into a small saucepan and sprinkle the gelatin over the top. Let stand for five minutes.
Put the raspberries in a large saucepan and warm over low heat, stirring occasionally, until thawed and a little juicy, about five minutes over a large bowl and press on the berries to extract all the juice. You should have 1-1/2 cups juice. Discard the seeds. Add the sugar to the juice and whisk to combine.
In a small saucepan, sprinkle the gelatin over 1/4 cup tepid water; let stand for five minutes.
Heat the gelatin mixture over medium-low heat, stirring frequently, just until dissolved, about two minutes. Remove the gelatin from the heat and stir into the raspberry mixture. Let stand, stirring occasionally, until the mixture has thickened to the consistency of raw egg whites, about 20 to 25 minutes. (If the mixture becomes too thick, gently warm it over a pot of boiling water, then cool, stirring, to the proper consistency.)
With an electric mixer, beat the cream in a large bowl to medium peaks (just barely stiff). Fold about one quarter of the whipped cream into the raspberry mixture to lighten it, and then fold in the remaining whipped cream. Pour the mixture into the prepared bowl. Refrigerate, covered, until set, at least eight hours, or overnight.
When ready to serve, make the chocolate shell.
Combine the chocolate, coconut oil, and salt in a medium microwave-safe bowl. Microwave for 15-second intervals, stirring well between each, until the mixture is smooth, one to one-and-a-half minutes. Let cool to room temperature, about 15 minutes.
Invert the dome onto a platter, and then remove the bowl and plastic wrap. Slowly pour about 1/2 cup of the cooled chocolate shell over the cold dome, guiding and gently smoothing it over the dome with the back of a spoon as you go. Let stand until the chocolate has hardened, five to ten minutes. (If the coating cracks, use the remaining chocolate to fill in and repair it.)
Decorate the dome as you wish with some of the fruit and mint. Run a large chef’s knife under hot tap water, then wipe dry. Use the hot knife, wiping it clean between cuts and rewarming it if necessary, to cut the dome into wedges. Serve with the remaining fruit and mint.