Heat the oven to 325°F (165°C). Spread pecans in one layer on a rimmed baking sheet. Toast 7–10 minutes, stirring halfway and checking from 6 minutes, until fragrant and slightly darker. Transfer to a cool plate. Optionally reserve 1–2 tablespoons for garnish.

Combine butter, brown sugar, the 1/3 cup topping cream, and salt in a small saucepan over medium-low heat. Stir until melted and smooth. Once small bubbles rise steadily, simmer gently 2–3 minutes, stirring. Remove from heat; add the topping vanilla and toasted pecans, except any reserved garnish.

Transfer to a shallow heatproof bowl. Cool about 25–30 minutes, stirring occasionally, until no longer warm but still spoonable. Allow more time if needed. Do not layer warm topping over the base.

While the topping cools, whip the cold 1/2 cup base cream to firm, glossy peaks in a clean bowl. In a separate bowl beat softened cream cheese smooth. Beat in powdered sugar and base vanilla, scraping the bowl. Stir in a spoonful of whipped cream, then gently fold in the rest.

Spread the base in an 8-inch shallow serving dish or 9-inch pie plate; refrigerate while the topping finishes cooling. Spoon fully cooled topping over the base and spread gently. Cover and chill at least 30 minutes.

Add any reserved nuts just before serving. Offer sturdy dippers and a serving spoon. If very firm, let the dip soften 10–15 minutes before serving, within the safe room-temperature limits in the notes.