Place 1 cup of blueberries, sugar, lemon juice and 1 tablespoon of water in a small saucepan over medium heat and stir to combine.
Bring the mixture to a simmer, stirring often until the berries soften and begin to break down, lightly mashing the berries to release their juice.
Add the remaining ½ cup of blueberries and cook for another minute or two until the mixture is thick and syrupy. Remove from heat and set aside to cool.
Meanwhile, in a small bowl, mix together mascarpone cheese, Greek yogurt, lemon zest and honey until smooth and spreadable. Set aside.
Toast bread. Spread half the mascarpone mixture on each slice of bread. Top each piece with a dollop of blueberry compote.
Before serving, drizzle each piece with honey and sprinkle with extra lemon zest if desired.