To up the orange flavour in the No-Churn Bitter Orange Ice Cream, and in the absence of fresh/frozen Seville oranges, could one, in addition to the sweet orange/lime mix, swirl in some bitter orange marmalade as well?
Nigella's No-Churn Bitter Orange Ice Cream (from NIGELLA BITES) is made with a combination of cream, icing (confectioners') sugar and the juice and zest from bitter Seville oranges. You can substitute a combination of regular sweet oranges and limes if Seville oranges are not available.
We suspect that you could add some bitter orange marmalade if you wanted, though it will change the texture of the ice cream with chunks of peel. The main issue will be how to dissolve the non-peel parts of the marmalade in the cream. We suspect that the best way to do this is to take about 150ml (2/3 cup) of the cream and warm it gently with the marmalade until the non-peel part of the marmalade has dissolved. Let this mixture cool completely and then chill it before adding it to the remaining cream and making the ice cream. You may also like to reduce the sugar very slightly if you use a marmalade, but this will depend on the type of marmalade you use and how sweet it is. However we would mention that as we have not tried this ice cream with added marmalade, we are unable to guarantee the results.