Puree the crème fraîche with all the other ingredients up to and including the pepper, set aside.
To cook the asparagus
Preheat the oven to 60 °C and warm a plate. Add the salt, sugar and butter to the boiling water. Add the green and white asparagus, return to the boil. Remove the pan from the heat, cover and allow to infuse for approx. 15 mins. Remove the asparagus, drain, transfer to the warm plate and keep warm.
Heat the oil in a frying pan. Fry the capers for approx. 5 mins. until crispy, stirring occasionally. Remove and drain on paper towels. Add the mint to the same pan, fry for approx. 30 secs. until crispy, drain. Drizzle the sauce over the asparagus, garnish with the capers and mint.