Prep your blueberries by tossing them with flour to coat them. Place the berries in a storage bag and freeze until the next day.
Prep your streusel topping by combining the ingredients until it's fully combined and large clumps form. Place in a storage bag and refrigerate for the next day.
For the muffins, combine all of your dry ingredients including the flours, sugar, cinnamon, salt, lemon zest, baking powder, and soda in a bowl and set them aside. Then, begin by creaming the butter at a medium speed for about a minute. Stop the mixer and scrape the bowl and paddle well. Start the mixer again and begin to gradually add in the sugar. Mix on medium speed for a minute or two until the sugar is combined.
Add in your molasses and honey all at once and mix for another minute at a medium-low speed. Stop the mixer and scrape the bowl and paddle well.
Pour your vanilla and eggs into a measuring cup and pour them both slowly into your batter. Mix until the egg is absorbed at a medium speed. Stop the mixer and scrape the bowl and paddle well.
Pour your buttermilk into a measuring cup. Starting at a low speed, add in about half of your dry ingredients. Then slowly pour in half of your buttermilk. Give it a moment to mix. Then add in the rest of your dry ingredients. Give it another moment to mix and then add in the last of your buttermilk. Give it just a few moments to mix until just combined. Don't overmix! Stop the mixer at this point and scrape down the bowl and paddle well.
Use a rubber spatula to get the bottom and sides of the bowl. Cover the bowl with plastic wrap and refrigerate for at least 24 hours.
The next day, remove your batter from the fridge and allow the batter to sit out on the counter for 10 minutes. During this time, preheat your oven to 425°F and prepare your muffin pan with liners and cooking spray. After 10 minutes, remove the berries from the freezer and pour them into your batter. Very gently fold in the berries just enough. Don't overmix.
Use a medium-sized cookie or ice cream scoop to portion out your batter. Remove the streusel topping from the fridge and generously add handfuls to the top of the muffins.
Place your muffins in the oven and immediately lower the temperature to 325°F. Bake for 35-40 minutes or until the streusel is cooked, the muffins are tall and golden brown. To test for doneness, use a skewer and poke at around the 30-minute mark. It should come out with a few moist crumbs. If it's wet, it needs to bake longer. If it comes out completely dry, that means the muffins are overbaked and dry.
Once the muffins are done cooking, allow them to sit in the pan for a couple of minutes before moving them to a cooling wire rack. Serve warm and enjoy! Best served the same day.