In a large skillet over medium heat, heat the olive oil until it shimmers. Add diced onion and cook for about 5 minutes, until onion begins to soften. Add ground beef and continue to cook until it’s uniformly brown. Add taco seasoning and cook until fully combined and heated through. Remove from heat and set aside.

Preheat oven to 400 degrees. Line a baking sheet with parchment paper. 

On a floured surface, unfold one sheet of the thawed puff pastry and roll out to roughly a 12″x12″ square (keep the other sheet in the fridge while you work so it doesn’t dry out or get too soft). Using a large biscuit cutter or 2/5-inch round cookie cutter, cut as many circles as you can fit (I get 12-14 per sheet). 

Place one heaping teaspoon of ground beef in the center of each circle, along with a sprinkle of cheese. Use your fingertips to fold the circle in half and gently seal the turnover. Further seal by using the tines of a fork to crimp the edges. Brush the top and sides of each turnover with the egg wash. 

Transfer the turnovers to the prepared baking sheet and bake for 15-17 mins, until golden brown. 

Remove second sheet of puff pastry from fridge and repeat the process. 

Cool turnovers on the baking sheet or cooling rack until ready to serve. These are great at room temperature, but if you want to serve them slightly warm, wrap them gently in foil and reheat in a very low (200-degree) oven. 

To make the dipping sauce, simply combine all ingredients and whisk until combined. Taste and adjust seasonings if needed. 

Pile turnovers on a plate or serving platter with a bowl of dipping sauce on the side. Garnish sauce with a few snipped chives or sprigs of parsley, if desired.