Place the flours, polenta, xanthan gum and butter in a food processor and whiz until the mixture resembles fine breadcrumbs, or rub in by hand in a large bowl. Stir in the sugar.
Add the egg and very gently mix in using a knife, adding enough cold water (probably a couple of teaspoons) to make a dough. Try not to let it become too wet. Knead for a couple of minutes, then wrap closely in clingfilm and chill for about an hour.
Meanwhile, place the sugar, butter and honey for the filling in a medium saucepan and heat until the sugar has dissolved. Leave to cool for 10 minutes.
Remove the dough from the refrigerator while the filling is cooking. Knead it on a surface dusted lightly with rice flour to soften it a little. Divide the dough into eight, then roll each piece out to a thickness of 2.5 mm (⅛ inch). Use to line eight individual 11.5 cm (4½ inch) pie tins, rolling the rolling pin over the top to cut off the excess dough.
Stir the chopped pecans and eggs into the filling mixture and pour into the pastry-lined tins. Arrange the pecan halves over the top, then place the tins in a preheated oven, 200°C (400°F), Gas Mark 6, for 15–20 minutes until the filling is firm. Remove the pies and leave to cool. Serve with crème fraîche.