Heat a small saucepan over medium heat. Add butter to the pan and stir frequently as it starts to melt and bubble. Look for little brown specks to start to appear and the color to change from yellow to a light amber, 3 to 5 minutes. Once it’s lightly browned, remove from the heat and transfer to a heatproof container to cool.

Preheat an oven to 350°F. In a spice grinder or mortar and pestle, grind sesame seeds until it's a powder. Add ground sesame seeds into a large mixing bowl along with cooled down brown butter, glutinous rice flour, sugar, kosher salt, baking powder, eggs, ricotta, sour cream, and vanilla extract. Mix until the batter is smooth, then pour into an oiled 9 inch cake tin. Bake for 45 minutes or until a toothpick comes out clean when stuck into the center. Once cooked, remove from oven and let it cool for about 30 minutes to let the mochi cake set.

Once the cake has cooled, cut into slices. If desired, make the optional topping by whisking together sour cream, ricotta, maple syrup, and kosher salt. Dollop the maple cream on top of each slice and add a halved strawberry to serve.