Combine the almonds, mint and honey in a food processor and process until smooth.
Preheat the grill for high heat direct grilling.
Brush the cut side of the peaches with canola oil and grill until golden brown and caramelized, about 1 1/2 minutes. Flip and continue grilling until just heated through, about 1 minute longer. Arrange the halves on a platter, cut-side up. Spoon some pesto into the pit hollows and then top with a little dollop of mascarpone. Garnish with torn mint leaves and serve immediately.