01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly with cooking spray.
02 - In a large bowl, whisk together flour, baking powder, baking soda, and salt until well combined. Set aside.
03 - In a separate bowl, mix vegetable oil and granulated sugar until incorporated. Beat in eggs one at a time, then add milk and vanilla extract, mixing thoroughly.
04 - Pour wet ingredients into dry ingredients. Stir gently with a spatula until just combined—batter should remain slightly lumpy. Avoid overmixing to prevent tough muffins.
05 - Gently fold chopped strawberries into batter until evenly distributed.
06 - In another bowl, blend softened cream cheese, granulated sugar, egg yolk, and vanilla extract until completely smooth and creamy.
07 - Spoon approximately 2 tablespoons of muffin batter into the bottom of each prepared muffin cup.
08 - Place 1 tablespoon of cream cheese filling in the center of each cup on top of the batter layer.
09 - Top with another tablespoon of batter to completely cover the filling. For a marbled appearance, gently swirl once with a toothpick without piercing to the bottom.
10 - Bake for 20 to 22 minutes until tops are lightly golden and a wooden pick inserted into the cake portion (not cream cheese center) comes out clean.
11 - Let muffins cool in the tin for 5 minutes before transferring to a wire rack to cool completely.