Preheat the oven to 350°F (175°C).

Mix the crushed pretzels, melted butter, and brown sugar until evenly combined.

Press the mixture firmly into the bottom of a 9x13-inch baking dish.

Bake for 10 minutes, then let the crust cool completely.

In a large bowl, beat the cream cheese, sugar, and vanilla until smooth and creamy.

Fold in the whipped topping until fully combined.

Spread the cream cheese mixture evenly over the cooled crust, sealing all the way to the edges to prevent the gelatin from leaking through.

Dissolve the peach gelatin in the boiling water and allow it to cool until slightly thickened but not set.

Fold the diced peaches into the cooled gelatin mixture.

Carefully spoon the peach mixture over the cream cheese layer.

Sprinkle chopped pecans over the top if desired.

Refrigerate for at least 4 hours, or until completely set.

Slice into squares and serve chilled.