Line a 9x9 inch baking dish with a piece of parchment paper. Lightly grease the parchment paper with butter. Set aside.
Preheat the oven to 350 degrees Fahrenheit.
In a small-sized bowl, stir together the flax meal and water. Let it rest for 10 minutes, occasionally stirring to ensure it doesn't separate. This mixture creates flax "eggs."
In a medium-large bowl, whisk the flour, cornstarch, baking soda, and salt. Set aside.
With a large mixing bowl, use a wooden spoon or rubber spatula to stir together the melted butter, brown sugar, molasses, and vanilla extract until well combined. Then, add in the flax "eggs." Stir until well combined.
Add about 1 cup of the dry mix at a time into the wet mixture. Stir until mostly combined. Repeat until all dry mix is incorporated into the wet mix and is evenly combined.
Add the 1 cup of vegan white chocolate chips and the 1/2 cup of chopped pecans into the batter. Use your hands to distribute them into the batter evenly.
Press the batter evenly into the greased baking dish.
Now, grab the pumpkin swirl mix you made earlier and divide it into 9 dollops across the top of the blondie batter. (So, make 3 rows of 3 dollops.)
Now, take a small (eating) spoon and lightly press/dip the pumpkin mix into the very top of the batter with the back of the spoon. Then, swirl the pumpkin dollops together, just ever so slightly. Do not over swirl or cover the entire top of the blondie batter with the pumpkin mix, or the pumpkin will get "lost" in flavor.
Sprinkle across the 2 tablespoons of white chocolate chips and 2 tablespoons of pecans.
Pop the prepared baking dish into the oven, on the middle rack, and bake for 30 minutes, rotating that pan half-way through.
If decorating, allow the blondies to cool down to room temperature completely. I also HIGHLY recommend chilling the blondies in the refrigerator overnight, as they will become the chewiest they can be.
When ready to cut, lift the parchment paper holding the blondies out of the pan. Place it on a cutting board and cut them into whatever size your heart desires. For picture purposes, I cut mine into 9 squares (3 rows by 3 rows.) However, they're pretty thick and filling, so I'd suggest cutting them into 16 squares (4 rows by 4 rows) instead.