Drain
peaches; reserve 1/2 cup (125ml) syrup.
Blend or process peaches and berries until
smooth; push through fine sieve, discard
seeds.
Pour peach
mixture into medium pan, add sugar, stir over heat
until sugar dissolves. Stir in blended corn flour and
reserved syrup, stir over heat until sauce boils and
thickens. Stir in liqueur.