How to Make It
Heat oil in a large high-sided skillet over high. Add mushrooms; cook, stirring often, until well browned, 2 to 3 minutes. Reduce heat to medium. Add shallot, thyme, onion powder, and garlic; cook, stirring often, until mushrooms release their liquid, about 3 minutes.
Add sugar, vinegar, half of tarragon, and salt. Increase heat to medium-high; cook, stirring often, until glazy, 2 to 3 minutes. Remove from heat; stir in remaining tarragon.
Spread cream cheese evenly on toast slices. Top evenly with mushroom mixture.