Preheat oven with 400˚F. Line a rimmed baking sheet with parchment paper or a silicone baking mat.
Lightly roll out the sheets of puff pastry. Cut each into 4 rectangles so you have 8 in total.
Use a knife to create a 1/2-inch border around each tart. Make sure that you do not cut all the way through the pastry. Use a fork to lightly pierce the center of each multiple times.
Place pastry pieces on prepared baking sheet. Set aside.
In a bowl, beat together cream cheese, thyme, basil, garlic, salt, and pepper until smooth.
Spread the cream cheese in the center of each tart in an even layer. Top with slices of tomatoes.
Lightly beat together the egg and water until combined. Brush on the edges of each tart.
Bake for 18 to 20 minutes, until golden brown and puffed up.
Garnish with cheese and basil, as desired. Serve warm.