Cook the sweet potatoes in steam like normal potatoes until soft. Then place in a large bowl and let cool down a little.
Now add the brown sugar, butter, salt and vanilla flavor and use a potato masher to form a uniform mass. Now fold in half of the nuts.
Then put the mixture in a greased baking dish and smooth the surface. Sprinkle these with the remaining nuts and spread the marshmallows on top. Bake the whole thing in the preheated oven at 190 ° C (convection) for about 25 minutes until the marshmallows are nice and brown.
Note: With the complete 175 g of sugar it can be very sweet for some tastes. So maybe stir in half of the mixture first and try and then leave it there or add more sugar, depending on your taste.