Preheat oven to 425. Line a muffin tin with muffin papers. Lightly oil the surface of the muffin pan.
In a small mixing bowl, combine the 1/2 cup brown sugar, 1/4 cup walnuts, 1/4 cup oats, 1 tsp cinnamon and 1/2 tsp cloves. Set aside.
Sift the 2 cups flour, 1.5 tsp baking powder, 1/2 tsp baking soda, and 1/4 tsp salt in a medium size bowl. Set aside.
In a stand mixer with the paddle attachment, or using a hand mixer, lightly beat the two eggs. Cream the 1/2 cup butter, 1/2 cup brown sugar, and 2 tbsp sugar with the eggs until just beaten. Mixture will look a bit lumpy, this is ok.
Add the dry mixture to the wet mixture in three separate batches, mixing each batch in till just incorporated. Add in the 2 tsp of vanilla and 1 tsp of lemon zest.
Stir in the 1.5 cups of blueberries.
Fill each muffin cup to the top with the muffin batter. Top each muffin with a bit of the streusel mix.
Bake at 425 for 15 minutes; reduce heat to 350 and bake for another 15 minutes. Muffins are done when a toothpick inserted in the middle comes out clean.
Let muffins cool before you take the muffin papers off.
Enjoy!