1. Preheat the oven to 425°F / 220°C. Line a muffin pan with 6 parchment liners.

Streusel

1. In a small bowl, melt the butter. Add in the brown sugar, flour, and cinnamon. Use a fork to mix the ingredients together, then set aside. The streusel will seem super buttery & become a cohesive dough, but will be able to be crumbled by the time we add it to the muffins.

Blueberry Muffins

1. In a medium sized mixing bowl, melt the butter. Whisk in the sugar, egg, vanilla and kefir until well combined.
2. Add in the flour, baking powder, baking soda, and salt. Use a rubber spatula to lightly fold the mixture until just a few flour streaks remain.
3. In a small bowl, toss the blueberries with 2 tsp. of flour. Then, add the blueberries into the batter and fold just until no flour streaks remain.
4. Now it's time to layer the muffins. Start by pouring ~2 tbsp. of muffin batter into the bottom of each muffin liner. Top with 1 tsp. of blueberry jam, followed by ~1 tbsp. of streusel.
5. Top with an additional ~3 tbsp. of muffin batter, 1 tsp. of blueberry jam, and the remaining streusel.
6. Bake the muffins at 425°F for 5 minutes. Without opening the oven door, reduce the temperature to 350°F / 175°C.
7. Bake for an additional 12-15 minutes, or until a toothpick inserted into the center of the muffins comes out clean.
8. Serve and enjoy!