Melt the butter in a small saucepan. Remove the pan from the heat and stir in the honey.
Sprinkle the pear slices with a little lemon juice as soon as they are cut to prevent them from discolouring. Line a baking sheet with foil and lay the pear slices on it. Brush the pears with the butter and honey mixture and cook under a preheated grill on its highest setting for 5 minutes.
Meanwhile, make the minted mascarpone. Lightly whisk the mint and granulated sugar into the mascarpone in a bowl.
Arrange the pear slices on 4 plates and top each with a spoonful of the minted mascarpone. Decorate with mint sprigs, then lightly dust with icing sugar and cinnamon and serve immediately.