To make the streusel topping for the muffins: To a small bowl, add the butter, sugars, spices, salt and flour. Mix with your hands until clumpy. Set aside.
To make the muffins: Preheat your oven to 350 degrees F. Place 9 muffin liners in your muffin pan.
To a large bowl, whisk together the rye flour, all-purpose, brown sugar, white sugar, baking powder, baking soda and salt. In a 2 cup measuring cup or medium bowl, whisk together the milk, melted butter, egg and vanilla extract. Create a well in the dry ingredients and in one batch, pour the milk and egg mixture. Mix just until you no longer see any flecks of flour. Be sure to not overmix (this will overdevelop the gluten and create tough muffins). Fill the 10 muffin liners about 3/4 of the way full with batter. Sprinkle the tops with the streusel, adding a bit more than you think you should add.
Transfer to the oven to bake for about 15 to 20 minutes, rotating them at the 7-minute mark, until a skewer when inserted into the centers comes out clean. Cool the muffins in their tin for 5 minutes and then transfer them to a cooling rack.
To make the strawberry butter, add the strawberries and sugar to a small saucepan, set over medium-low heat. Cook until the strawberries have softened and release its juices and a syrup forms, about 3 to 4 minutes. Run the mixture through a strainer, discarding any pulp. In the bowl of a stand-up mixer with the paddle attachment, add the butter, 2 tablespoons of strawberry syrup, salt and freshly ground pink peppercorns. Mix until completely incorporated. Serve alongside the muffins