Cut the Brie into small bits. Toss both the Brie and blue cheese with the cornstarch.
Bring the wine and the mint to a simmer. Reduce by half, remove the mint and stir in one-third of the cheese mixture at a time until fully blended. Thin the mixture out as necessary with the heavy cream.
Skewer the fruits and arrange alongside the biscuits so that everyone has a selection. Dip the fruits and biscuits in the fondue.