Preheat the oven to 180C (350F). Spray a 23cm/9in springform cake tin with cake release and line the bottom with baking paper.
Mix the eggs, sugar, melted butter and pumpkin together in a big bowl.
Add the flour, soda, pumpkin spice and salt and use a balloon whisk to mix everything together until smooth.
Pour the batter into the prepared cake tin and smooth.
Bake for 45-50 minutes, covering the cake with foil if it is browning too much. The cake is ready when a skewer insterten in the centre comes out clean and the cake is coming away from the sides of the tin.
Cool for 10 minutes in the tin then transfer to a wire rack to cool completely.
Prepare the toffee sauce. Put the butter andsugar in a small saucepan and whisk together over medium heat until the butter is completely melted and sugar has dissolved.
Add the yoghurt or cream (take care as the toffee might sputter), vanilla and salt and boil for one minute. Leave to cool slightly.
Beat the cream cheese, brown sugar and spice together using a hand or stand mixer until smooth.
Spread the frosting over the cake and drizzle with the toffee sauce.