Preheat oven to 350°F (175°C) and grease a 9x11 inch baking dish.
In a bowl, whisk the egg and monkfruit sweetener.
Add yogurt and mix until smooth.
Stir in flour, baking powder, and salt.
Pour in milk and mix until batter is smooth.
Pour batter into baking dish, then scatter blueberries over the top.
In a separate bowl, mix crumble ingredients with a fork until crumbly.
Sprinkle crumble over blueberries and batter.
Bake for 45–60 minutes, until the center is set and no longer jiggles.
Let cool for better texture—or enjoy warm and gooey!