Combine Rice Chex and chopped pecans in a large mixing bowl.
Combine brown sugar, butter and corn syrup in a microwave-safe bowl and microwave on high for 2 minutes, stirring after 1 minute.
Remove from microwave and whisk in baking soda.
Pour over cereal mixture and gently toss until cereal and pecans are evenly coated.
Spread mixture onto a baking sheet lined with waxed paper; let cool.
In a microwave-safe bowl, combine vegetable oil and white chocolate chips. Cook on high for 2-3 minutes, stirring every minute until smooth.
Drizzle melted white chocolate over cereal mixture and refrigerate until set.
Break into pieces and serve.
Store in an airtight container.
Notes
If you don't have room in your fridge to let this set up, you can leave it out on your counter. It will set up faster in the fridge, but it also works to just leave it out.