1. Preheat the oven to 170˚C, gas mark 3; lightly grease and line the base and sides of a 20cm cake tin. In a large mixing bowl, use electric beaters to cream the butter and honey together, until light and fl uffy. Beat in the egg yolks and lemon zest, then the almonds, polenta, baking powder, salt and thyme leaves.
2. In a separate, clean bowl, with clean beaters, whisk the egg whites to stiff peaks. Gently fold into the polenta mixture, being careful to retain as much air as possible but making sure all the egg white is mixed in. Tip into the cake tin and bake for 45 minutes, until golden and cooked through (cover loosely with a sheet of foil if it browns too quickly). Cool the cake for 15 minutes in the tin, then remove and leave to cool completely on a wire rack.
3. When ready to serve, whisk the double cream to very soft peaks, then whisk in the yogurt and vanilla bean paste; set aside. Heat the syrup ingredients in a small pan until bubbling, then pour over the cake. Top with a sprig of thyme, slice and serve with the cream.