For the strawberry base: Put the strawberries
in a bowl, add the sugar and gently stir to combine. Let the berries sit at room temperature for 30 minutes, until they start to soften and release their juices.
Transfer the mixture to a medium nonreactive saucepan
, add the jam and cook over medium-high heat until slightly softened. Coarsely mash
the berries using a potato
masher or the back of a fork and continue cooking, stirring occasionally, until the mixture thickens to a jam-like consistency, about 20 minutes. Remove from the heat and stir in the lemon juice
. Transfer to a bowl, cover and refrigerate until cold and thickened further, at least 2 hours.
For the milkshake: Combine the milk and 1/2 cup strawberry base in the blender
and blend for 5 seconds. Add the ice cream
and blend until smooth, about 10 seconds. Top with more strawberry base, the Sugar Biscuit and a strawberry for garnish
, if using.