In a small bowl, combine 1/4 cup brown sugar and 1/2 teaspoon ground cinnamon.
Place 4 slices of thinly sliced bacon onto a cooling rack that has been laid on top of a foil lined cookie sheet. Sprinkle liberally with brown sugar mixture; use fingers to press mixture into the bacon.
Bake for 15-20 minutes, or until bacon is crispy, but not burnt. Remove pan from oven and carefully transfer bacon slices to a cutting board to cool slightly before chopping into small pieces.
Make Bacon Streusel
In a medium bowl, combine candied bacon, brown sugar, pumpkin pie spice and flour. Stir to combine; set aside.
Make Pumpkin Muffins
Reduce heat in oven to 350°.
Use an electric hand or stand mixer to beat butter and cream cheese at medium speed until creamy. Gradually add sugars, beating until light and fluffy. Add eggs, 1 at a time, beating just until blended after each addition. Add pumpkin and vanilla and mix until combined.
Stir together flour and next 4 ingredients; gradually add to butter mixture, beating at low speed, just until combined. Avoid over mixing or your muffins will be tough. Use a spoon to stir in nuts by hand.
Spoon batter into 2 lightly greased or paper lined (12-cup) muffin pans, filling two-thirds full. Sprinkle with Bacon Streusel.
Bake at 350° for 18-23 minutes, or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 5 minutes; remove from pans to wire racks to cool completely.