Preheat oven to 400 degrees F. Line a baking sheet with foil then place a wire rack on the baking sheet.
To prepare streusel, combine 3 tablespoons brown sugar, 2 teaspoons water, and pepper in a small bowl. Spread mixture evenly over both sides of bacon. Place coated bacon on rack and bake at 400 degrees F for 18 minutes or until done. Cool and finely chop.
Combine oats and 1 tablespoon flour in a small bowl. Stir in butter. Stir in 2 tablespoons chopped bacon reserving remaining bacon. Set aside.
Reduce oven temperature to 350 degrees F. Line 12 muffin cups with paper liners.
To prepare muffins, combine 225 grams flour, remaining bacon, 1/2 cup brown sugar, baking powder, salt, and baking soda in a large bowl. Stir well. Combine beer, oil, vanilla, and egg in another bowl, gently stirring with a whisk. Add beer mixture to flour mixture, stirring just until combined. Evenly divide batter among 12 muffin cups. Sprinkle streusel evenly over batter.
Bake at 350 degrees F for 18 minutes or until a wooden pick inserted in the center of muffins comes out clean. Cool in pan for 5 minutes. Remove muffins from pan. Serve warm, or cool completely on a wire rack.